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Lincoln Park High School
Integrated Science
NAME: ________________________
PERIOD: ____
The WHAT,
WHY, and HOW
of Chemistry
Topic 09:
Periodic Trends
“I believe we are on an irreversible trend toward more freedom and democracy –
but that could change.”
-Dan Quayle
Lincoln Park High School presents:
The WHAT, WHY, and HOW of Chemistry
Topic 09
Periodic Trends
Created and edited by James S. Galinski, February 2016
Material adapted from:
Addison-Wesley Chemistry – Volume 5 – Chapter 14
When some people hear the word “trend,” they might think of some shared behavior that sweeps
through the population for a short period of time. This fashion choice or hairstyle or collectible catches
on, but fades away when the novelty is gone.
Bell-Bottoms
The Mullet
Beanie Babies
The Pet Rock
This idea more accurately fits the word “fad” than “trend.” Another meaning of trend is when someone
or something is the subject of many posts on a social media website within a short period of time. This
also is more like a fad, due to its fleeting nature. The word trend, as it applies to the context of science,
is a general direction in which something is developing or changing. It is usually more long term and
universal than a fad, and not just an easily reversible, momentary blip. By using trends, a scientist can
extrapolate data and predict what is not yet known.
By that definition, the national debt is a trend. By looking at the data, we can predict what is going to
happen in the future. The debt seems to be increasing, with no signs of stopping.
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Rising temperatures around the globe have raised concerns about climate change and global warming.
Of course, not all trends occur in a simple straight-line fashion. Some first rise and then fall, or fall first
and then rise.
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Whether the data is the amount of money owed by the United States, the temperature of the Earth, or
the physical size of cellular phones, the trends are all patterns in numbers. You have undoubtedly
worked with numerical patterns before at some point in your education. Use what you know to
complete the following numerical series:
1
3
5
7
9
13
17
19
Pretty easy, right? Sometimes, numerical patterns are arithmetic. That is, they change by the same
amount with every step. However, that is not always the case. Use what you know to complete the
following series:
1
2
4
8
16
32
128
512
This series of numbers is geometric. The amount it changes by increases with every step.
Sometimes, it is important for us to try to make sense of a jumbled set of data. Take the following
numbers, and put them in some kind of order in the boxes on the right:
23
12
26
1
4
28
15
7
The most instinctive, logical way to do this is to put them in numerical order.
However, what if the numerical information you needed to organize could be interpreted in two ways?
Your instructor will give you a set of playing cards. By organizing them, your job is to figure out what
card is missing.
Which card is missing from your set of cards?
In the space provided, briefly explain how you arrived at that conclusion.
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Let’s reconsider the numbers from earlier, but adding a new dimension of classification. Now, the
numbers are associated with a letter or symbol, not unlike the chemical symbols in the periodic table.
Try to fit the eight squares into the 3×3 grid on the right. You can either cut the squares out, or rewrite
the symbols into the grid.
Blue
Blue
Green
Se
Te
N
1
23
28
Red
Red
Green
Et
T
He
4
15
7
Red
Blue
R
Pa
26
12
Rewrite or glue the symbols into this grid:
What choices did you make as you organized the squares? If you left a blank space, why did you do so?
Do you see the hidden message in the 3×3 grid? What do the symbols spell out?
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Your instructor will give you a deck of colored cards. The deck is missing one card. Perform the
following steps to find the identity of the missing card.
1. Look through the set of cards. Write a general description of the properties of the cards.
2. Place all the cards in a logical sequence in one long row. Describe the property of the cards you
used to do this.
3. Keeping the cards in the same order from step 2, arrange the cards in several rows so the each card
in a column has a common property with the other cards in the same column. In other words,
decide where to break the original arrangement to begin each new row so a pattern results.
4. It may be impossible to keep the cards in the same original order and have all the cards in a column
with a common property. Discuss which property is more appropriate for classifying the cards –
the property used to sequence the cards in a row, or the common property of the cards in a column.
Arrange the cards appropriately.
5. Once you and your partner have finalized the arrangement of cards, describe the resulting twodimensional classification system in the following box, and note any exceptions to the pattern.
6. One card is missing. Predict the properties (color and number) of the missing card.
7. Return the cards as instructed by the teacher. Get the missing card from your teacher. Find out if
your prediction was correct.
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Dimitri Mendeleev created the first periodic table in the 1800s. He listed
the elements in columns in order of increasing atomic mass. He then
arranged the columns so that the elements with the most similar
properties were side by side. Mendeleev left blank spaces in the table
because there were no known elements with the appropriate properties
and masses.
On the left, you will find
Mendeleev’s periodic table.
Notice that there are several
question marks next to
some of the atomic mass
numbers. Mendeleev was
not aware of all of the
elements that scientists
know about today. Using his
table, he was able to predict
the existence of some thenstill-unknown elements.
In 1913, Henry Moseley determined the atomic number of the atoms of the elements. Moseley
arranged the elements in a table by order of atomic number instead of atomic mass. That is the way the
periodic table is arranged today.
The horizontal rows of the modern
periodic table are called periods. The
properties of the elements within a
period change as you move across it
from element to element. The pattern
of properties within a period repeats,
however, when you move from one
period to the next. This repetition is
known as periodic law.
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Each vertical column of the periodic table is called a group or family. The elements in any
group of the periodic table have similar physical and chemical properties.
Without the help of the periodic table, it would be difficult to learn and remember the chemical and
physical properties of the more than 100 elements. Instead of memorizing their properties separately,
you need only learn the general behavior and trends within the major groups. This gives you a useful
working knowledge of the properties of most elements.
What two characteristics of elements did Mendeleev use to construct his periodic table of the elements?
Name two elements in the periodic table that have properties similar to those of the element calcium.
How did Moseley’s arrangement of the elements differ from that of Mendeleev?
As was already discussed, a vertical column in the periodic table is called a group. The first vertical
column in the table is called Group 1A. It is composed of the elements H, Li, Na, K, Rb, Cs, and Fr. The
second vertical column, starting with Be, is called Group 2A.
The Group A elements
in the periodic table
are known as the
representative
elements, or main
groups. They are
composed of the first
two, and the last six
columns of the
periodic table.
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The metallic elements are grouped on the left side of the periodic table. Metals are elements that have
a high luster when clean and a high electrical conductivity. They are ductile (can be drawn into wire)
and malleable (can be beaten into sheets). Most of the elements are metals. They include the
transition metals, which are the B group elements, located in the middle of the periodic table. They also
include the inner transition metals, which are commonly known as the Lanthanides and Actinides, and
are usually found detached from the periodic table and listed separately.
The nonmetals are elements that are nonlusterous and are poor conductors of electricity. Some of these
elements are gases, others are brittle solids, and one, bromine, is a liquid at room temperature. The
nonmetals are located on the right side of the periodic table. A jagged invisible “staircase” separates
the metals from the nonmetals. The staircase starts between Boron and Aluminum, and runs right and
down repeatedly.
Look at the periodic table above, and make sure you can identify the representative elements, the
transition elements, the metals, the nonmetals, and the invisible “staircase” that divides them.
Relate group, period, and transition metals to the periodic table.
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Identify each element as a metal or nonmetal.
Element
Metal or
Nonmetal?
Gold
Fluorine
Sodium
Barium
Oxygen
Iron
Which of the elements in the preceding question are representative elements?
As was mentioned earlier, the vertical columns of the periodic table are called groups or families. This
designation is used because elements in any group of the periodic table have similar physical and
chemical properties. The reason for this is that the outermost electrons of atoms in the same family are
organized the same way. The outermost electrons are the ones that interact with the universe at large.
If the outermost electrons are similar, then the behavior is similar.
The electron configuration and the nature of the outermost electrons can be easily determined by using
the periodic table. If you recall, the identity of the outermost electrons is tied to an atom’s geographic
location in the table, and the regions of the table can quickly be identified as “blocks” based on which
electrons are on the outside.
s-block
d-block
p-block
1s
1s
2s
2p
3s
3p
4s
3d
4p
5s
4d
5p
6s
4f
5d
6p
7s
5f
6d
7p
Hopefully, you remember how to determine the electron configuration of atoms using the periodic
table. If not, the following game will help refresh your memory.
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Periodic Table BATTLESHIP
Inspired by the Academy Award Winning 2012 Motion Picture*
For 2 Players
Object of the game
Be the first to sink all 5 of your opponent’s ships.
Requirements
Periodic Table Battleship – Attack Grid
Periodic Table Battleship – Defense Grid
5 different colored pencils, crayons, or markers
Prepare for battle
You and your opponent sit facing each other, with something blocking each of you from seeing the
other’s Attack and Defense Grids.
Choose one colored pencil or crayon to represent each of your ships. At the bottom of your defense
grid, fill in the squares that correspond with each ship.
Place your fleet of 5 ships on your ocean grid. To place each ship, lightly fill in the appropriate squares
on your defense grid, with the same color you used to identify your ships in the squares at the bottom
of the page. Your opponent does the same.
Rules for placing ships:



Place each ship in any horizontal or vertical position, but not diagonally.
Do not place a ship so that any part of it overlaps the edge of the grid or another ship.
Do not change the position of any ship once the game has begun.
How to play
Decide who will go first. You and your opponent will alternate turns, calling out one shot per turn to
try and hit each other’s ships.
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Call your shot!
On your turn, pick a target on your Attack Grid, and call out its location by electron configuration.
When you call a shot, your opponent must identify the element on his/her Defense Grid, and tell you
whether your shot is a hit or a miss.
It’s a hit!
If you call out a shot location that is occupied by a ship on your opponent’s Defense Grid, your shot is a
hit! Your opponent tells you which ship you have hit (cruiser, submarine, etc.). Record your hit by
drawing an X in the appropriate square on your Attack Grid.
Example: You and Alex are the players. It’s your turn.
Your call: “4d9.”
Alex answers: “Ag. Silver. Hit. Cruiser.”
You place an X in coordinate 4d9 of your Attack Grid. Alex places an X over
the corresponding square of his/her Defense Grid.
It’s a miss!
If you call out a shot location not occupied by a ship on your opponent’s Defense Grid, it’s a miss.
Record your miss by drawing a circle in the corresponding target square on your Attack Grid so that
you won’t call this shot again.
Example: Now it’s Alex’s turn.
Alex calls: “5s2.”
You answer: “Sr. Strontium. Miss.”
You place an X in coordinate 5s2 of your Defense Grid. Alex places an O over
the corresponding square of his/her Attack Grid.
Play continues in this manner, with you and your opponent calling one shot per turn.
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Sinking a ship and winning the game
Once all the holes in any one ship are filled with Xs, it has been sunk. The owner of the ship must
announce which ship was sunk.
If you’re the first player to sink your opponent’s entire fleet of 5 ships, you win the game! Remember,
the goal is to not only sink your opponent’s ships, but to refamiliarize yourself with the layout of the
periodic table. Have fun!
*Note to self: I’m pretty sure that Battleship won the Oscars for Best Picture, Best Original Screenplay,
and Best Supporting Actress (Rihanna). But, I’m not 100% sure. I should definitely look
that up before students see this. If I’m wrong, that could be embarrassing!
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Periodic Table Battleship – Attack Grid
s-block (n)
p-block (n)
d-block (n-1)
n=1
1s1
1s2
n=2
2s1
2s2
2p1 2p2 2p3 2p4 2p5 2p6
n=3
3s1
3s2
3p1 3p2 3p3 3p4 3p5 3p6
n=4
4s1
4s2 3d1 3d2 3d3 3d4 3d5 3d6 3d7 3d8 3d9 3d10 4p1 4p2 4p3 4p4 4p5 4p6
n=5
5s1
5s2 4d1 4d2 4d3 4d4 4d5 4d6 4d7 4d8 4d9 4d10 5p1 5p2 5p3 5p4 5p5 5p6
n=6
6s1
6s2 5d1 5d2 5d3 5d4 5d5 5d6 5d7 5d8 5d9 5d10 6p1 6p2 6p3 6p4 6p5 6p6
n=7
7s1
7s2 6d1 6d2 6d3 6d4 6d5 6d6 6d7 6d8 6d9 6d10 7p1 7p2 7p3 7p4 7p5 7p6
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Periodic Table Battleship – Defense Grid
s-block (n)
n=1
H
n=2
Li
n=3
n=4
p-block (n)
d-block (n-1)
He
Be
B
C
N
O
F
Na Mg
Al
Si
P
S
Cl Ar
K
Ca Sc Ti
Cr Mn Fe Co Ni Cu Zn Ga Ge As Se Br Kr
n=5
Rb Sr
n=6
Cs Ba Lu Hf Ta W Re Os
n=7
Fr Ra Lr Rf Db Sg Bh Hs Mt Ds Rg Cn
Aircraft Carrier
Y
V
Ne
Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te
Battleship
Periodic Trends
Ir
I
Xe
Pt Au Hg Tl Pb Bi Po At Rn
Cruiser
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113
Fl
115
Submarine
Lv
117 118
Destroyer
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The vertical columns of the periodic table are called families. Once again, this is because the elements
in those columns have the same outermost electron configuration. This means that when we look
down a column in the table, we will see elements that behave in a fashion similar to each other.
Consider the alkali metals, the first column of the periodic table. They each have one electron in their
outermost energy level.
Element
Hydrogen
Electron Configuration
1s1
Lithium
1s22s1
Sodium
1s22s22p63s1
Potassium
1s22s22p63s23p64s1
Rubidium
1s22s22p63s23p64s23d104p65s1
Cesium
Francium
1s22s22p63s23p64s23d104p65s24d105p66s1
1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p67s1
Because the outermost electrons are arranged the same way, these elements interact with the universe
in the same way. The elements in this family, for instance, have a violent reaction with water. The
reactivity increases as we move down the periodic table.
Lithium
Sodium
Potassium
Francium
Bubbling, fizzing
More vigorous, flames
Explosive reaction
The End of Days
Since the chemical and physical properties of elements in a family are similar, we can look down a
column in the periodic table and see how those properties change. There are many trends that we can
observe, measure, and even predict.
First, let’s take a look at the density of elements in the p2 column.
Element
Electron Configuration
Carbon
1s22s22p2
Silicon
1s22s22p63s23p2
Germanium
Tin
Lead
1s22s22p63s23p64s23d104p2
1s22s22p63s23p64s23d104p65s24d105p2
1s22s22p63s23p64s23d104p65s24d105p66s24f145d106p2
You will be given samples of Silicon, Tin, and Lead. All of these elements are in the same column of the
Periodic Table, and have similar properties. Using a balance, you will find the mass of a sample of each
element. Using a graduated cylinder and some water, you will then find the displacement volume of
each sample. Then, you can determine the density of each element using calculations you have already
mastered.
What does the term “displacement volume” mean? How is volume to be measured in this lab?
Does the size of the sample matter? Why or why not? You might want to consider the definition of
density as you formulate an answer.
Your goal for this lab is to use the measured densities of the other elements to identify a trend, and to
use that trend to estimate the density of Germanium, element #32. Then, compare the experimental
data to the literature values for the densities of these elements. Watch for patterns. Use the data tables
on the next page to guide your experimental approach.
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Density is a Periodic Property – The p2 Elements – Raw Data
Symbol
Element
Si
Silicon
Ge
Germanium
Sn
Tin
Pb
Lead
Period
Qualitative Observations
Mass
(g)
Volume
(cm3)
Density is a Periodic Property – The p2 Elements – Processed Data
Symbol
Element
Si
Silicon
Ge
Germanium
Sn
Tin
Pb
Lead
Period
Measured Density
(g/cm3)
Literature Density
(g/cm3)
Estimated
Density:
Take a moment to look up the literature densities for the elements you measured in lab. Write the
densities in the table above.
On the next page, plot the densities you measured in lab against the period number. Identify the trend
in density as you move down the periodic table through the p2 column. Compare your density trend to
that of the literature data. The literature data has already been plotted for you.
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Density (g/cm3)
12.5
Density vs. Period
07
12.0
11.5
11.0
10.5
10.0
9.5
9.0
8.5
8.0
7.5
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Periodic Trends
7.0
×
06
6.5
Period
×
05
6.0
5.5
5.0
4.5
×
4.0
03
3.5
×
3.0
02
×
04
2.5
2.0
01
Density is only one of the many properties of elements that manifests itself as a trend in the periodic
table. There are many others which we need to know about. Let’s begin with size, or atomic radius.
According to atomic theory, an atom consists of a densely packed positive nucleus, surrounded by a
cloud of electrons. The electrons are organized into energy levels, with lower energy levels being close
to the nucleus, and higher energy levels being farther away. The size of an atom, or the atomic radius,
is the distance from the nucleus to the outermost electrons. It doesn’t matter that there are many
energy levels in between. Let’s look at how the size of an atom changes as we move down through the
periodic table.
Let’s consider two different elements, lithium and sodium.
Lithium has an electron configuration of 1s22s1. Its electrons fill the atomic orbitals like so.
The outermost electron in lithium is the 2s1 electron, in the second energy level.
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Sodium, on the other hand, has an electron configuration of 1s22s22p63s1. This means it has an electron
in the third energy level. Because it has an electron that is in energy levels further away from the
nucleus, the electron cloud must be bigger, and the sodium atom therefore must be bigger than the
lithium atom.
Atomic radius generally increases as you move down a group of the periodic table. As you descend,
electrons are added to successively higher principal energy levels and the nuclear charge increases.
The outermost orbital is larger as you move downward. Atoms at the bottom of the table are bigger
than atoms at the top.
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Now, to demonstrate this, consider the elements sulfur and oxygen. They are both in the same family.
Identify which element is larger, and conclusively demonstrate why that is in the space provided. Use
the diagrams that have been provided for you.
Atoms at the bottom of the table are larger. This phenomenon is rather intuitive. But what happens as
we move left or right? The answer to that question is not as intuitive and obvious. To find the answer,
we will have to solve the riddle of the “Alien Periodic Table”.
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Alien Periodic Table Activity
Organizing elements into a table is not just a human activity. On the planet Gleeglaxx, in the
Zzorgonax Nebula, scientists gather information about the elements they know of, and try to
find patterns in their arrangement, just as Mendeleev and Moseley did many years ago here on
Earth. For this activity, imagine that you are a Gleeglaxxian scientist, and if you manage to
solve the puzzle of the periodic table, you will become famous, from the hills of Fleembrizz all
the way to the crimson shores of Jeebo.
On the following few pages, you will find periodic table entries containing all elements known
to the Gleeglaxx scientific community. These elements have been identified by name and
chemical symbol, atomic radius (which is measured in parbs, a common unit of measurement
on Gleeglaxx), and also by chemical and physical properties. On the pages following that, there
are some larger rectangles representing each of the chemical and physical properties that can
be used to categorize the elements.
First, cut everything out. Cut out the individual squares and the larger rectangles.
Then, separate the elements into families, based on their chemical and physical properties.
Next, use the atomic radius of each element to decide how the elements will be placed in a
family. Remember, size increases as you move down through the periodic table. When you
have figured the order out for a family, glue the element squares onto the family rectangle.
Finally, when you have completed the family rectangle for each chemical family, try to
determine how they are related to each other. Use atomic radius to guide you. Move the
family rectangles around until you discover the correct order.
Does radius increase as you move to the right? Does it decrease? Legend has it that when
properly arranged, the Gleeglaxxian periodic table will reveal an important hidden message to
anyone looking at it. Hopefully, you will be up to the task. When you have succeeded, tape the
columns together to construct the Gleeglaxxian periodic table.
Good luck, or as they say on Gleeglaxx, “Gortu Frambuline!!”
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Ra
Razaquine
le
legumbria
us
ha
Atomic Radius = 104 parbs
Reacts with Doop
Atomic Radius = 176 parbs
Shiny
Atomic Radius = 82 parbs
Dissolves in Iidrine
Atomic Radius = 142 parbs
Dissolves in Yorba
ea
es

easement
esteemo
Frownium
ge
Atomic Radius = 53 parbs
Soft and squishy
Atomic Radius = 39 parbs
Inert liquid
Atomic Radius = 126 parbs
Reacts with Doop
Atomic Radius = 124 parbs
Explosive
Ri
Mo
nc
De
Atomic Radius = 131 parbs
Shiny
Atomic Radius = 85 parbs
Dissolves in Yorba
Atomic Radius = 152 parbs
Shiny
Atomic Radius = 75 parbs
Reacts with Frownium
Yo
Yorba
e
eeequay
cr
N
Atomic Radius = 104 parbs
Dissolves in Iidrine
Atomic Radius = 147 parbs
Reacts with Doop
Atomic Radius = 68 parbs
Dissolves in Yorba
Atomic Radius = 96 parbs
Inert liquid
!!
Zowie!!
u
ummagumma
Th
Thoronite
s
sizzeleen
Atomic Radius = 115 parbs
Inert liquid
Atomic Radius = 93 parbs
Reacts with Frownium
Atomic Radius = 58 parbs
Inert liquid
Atomic Radius = 47 parbs
Explosive
Rigobertoolmos
Mojomoto
Periodic Trends
usurpine
ncqwrxztz
crudd
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harharine
gesetz
Degrasso
Nougat
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o
ue

uette
Smileyum
Atomic Radius = 79 parbs
Inert liquid
Atomic Radius = 94 parbs
Soft and squishy
Atomic Radius = 102 parbs
Explosive
Atomic Radius = 151 parbs
Reacts with Frownium
I
D
di
r
Iidrine
Doop
dieeezazzle
rrrrroca
Atomic Radius = 162 parbs
Reacts with Doop
Atomic Radius = 100 parbs
Dissolves in Yorba
Atomic Radius = 98 parbs
Shiny
Atomic Radius = 138 parbs
Soft and squishy
ng
To
Tootsie
g
ganabanalanamanaschmoo
ar
Atomic Radius = 111 parbs
Soft and squishy
Atomic Radius = 65 parbs
Explosive
Atomic Radius = 127 parbs
Dissolves in Iidrine
Atomic Radius = 165 parbs
Dissolves in Iidrine
re
resutspeck
a
ahsweepay
uc
T
Atomic Radius = 143 parbs
Dissolves in Iidrine
Atomic Radius = 138 parbs
Reacts with Frownium
Atomic Radius = 183 parbs
Reacts with Doop
Atomic Radius = 87 parbs
Explosive
As
Aspartabalaba
si
signatoria
ve
ht
Atomic Radius = 110 parbs
Shiny
Atomic Radius = 127 parbs
Dissolves in Yorba
Atomic Radius = 73 parbs
Soft and squishy
Atomic Radius = 116 parbs
Reacts with Frownium
ohno
ngptingo
Periodic Trends
C
Cud
ucuzu
velour
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arfosibe
Tico
htgrwxtz
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Reacts with Frownium
FAMILY RECTANGLE
Explosive
FAMILY RECTANGLE
Inert Liquid
FAMILY RECTANGLE
Reacts with Doop
FAMILY RECTANGLE
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Soft and Squishy
FAMILY RECTANGLE
Dissolves in Yorba
FAMILY RECTANGLE
Dissolves in Iidrine
FAMILY RECTANGLE
Shiny
FAMILY RECTANGLE
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Atomic radius decreases as you move to the right due to increasing nuclear charge. To clarify, let’s
consider two elements from the second period of the periodic table, lithium and nitrogen.
Lithium is all the way on the left side of the periodic table. It has three protons, and an electron
configuration of 1s22s1. This means it has electrons in the first two energy levels.
Nitrogen is on the right side of the periodic table. It has seven protons, and an electron configuration of
1s22s22p3. This means it also has electrons in the first two energy levels.
If you recall, an atom’s radius is the distance from the densely packed positive nucleus to the outermost
electrons. Remember also that most of the atom is empty space, and that the positive charge of the
nucleus pulls at the tiny, negative outer electrons. Since lithium and nitrogen both have their outer
electrons in the same energy level, the difference-maker in terms of size must be the number of protons
in the nucleus doing the pulling. Because nitrogen has seven protons while lithium only has three,
nitrogen’s nucleus does a more effective job of pulling in electrons, and the nitrogen atom is smaller. Or
simply, atomic radius decreases as you move to the right due to increasing nuclear charge.
Lithium – 1s22s1
3 protons – 1 electron in the outer shell
Nitrogen – 1s22s22p3
7 protons – 5 electrons in the outer shell
The trend for size/radius is generally more pronounced as you move through a group (up or down)
than through a period (right or left). This is because of the addition of new energy levels as you move
down the table. An up/down move in the periodic table is generally a more important change in
atomic size than a left/right move.
Periodic Trends
Page 35 of 62
Atomic Radius (Å)
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
1.4
1.3
1.2
1.1
1.0
0.9
0.8
0.7
0.6
0.5
02
0.4
0.3
01
×
×
03
04
05
06
07
08
09
Atomic Radius vs. Atomic Number
10
11
12
13
14
15
Atomic Number
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
Periodic Trends
Page 36 of 62
On the previous page, there is a graph. Using the following data, plot the values for atomic radius on the
graph. After you have plotted the points, use a ruler to connect them in sequence.
Atomic
Number
Atomic
Radius
(Å)
Atomic
Number
Atomic
Radius
(Å)
Atomic
Number
Atomic
Radius
(Å)
Atomic
Number
Atomic
Radius
(Å)
01
02
03
04
05
06
07
08
09
0.3
0.9
1.5
0.9
0.9
0.8
0.7
0.7
0.6
10
11
12
13
14
15
16
17
18
1.1
1.9
1.6
1.4
1.2
1.1
1.0
1.0
1.5
19
20
21
22
23
24
25
26
27
2.3
2.0
1.6
1.5
1.3
1.3
1.3
1.3
1.2
28
29
30
31
32
33
34
35
1.2
1.3
1.3
1.2
1.2
1.2
1.1
1.1
You might be wondering about the symbol used as a measurement of radius in these tables. That
symbol, Å, is the symbol for angstrom, a unit of length that is equal to 1 × 10−10 m in length.
On your diagram, label the following elements by writing their elemental symbol next to the
appropriate plot point.
Atomic
Number
Element
Symbol
1
H
3
Li
9
F
11
Na
17
Cl
19
K
35
Br
Now, consider the elements you just identified, and their positions in the periodic table. What pattern
do you see?
Use your graph to extrapolate the answer to the following question. Rubidium is element 37, and it is
in the same family as Li, Na, and K. What will the atomic radius of Rubidium be?
Periodic Trends
Page 37 of 62
For each of the following pairs, circle the atom that is larger. On the right, circle the correct reason for
your answer. Use the periodic table to assist you.
Sodium
or
Magnesium
Aluminum
or
Sulfur
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
Lithium
More occupied energy levels
or
Lower nuclear charge
Silicon
or
Rubidium
More occupied energy levels
Oxygen
or
Strontium
or
Zirconium
More occupied energy levels
or
Lower nuclear charge
Bromine
or
Arsenic
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
Chlorine
More occupied energy levels
or
Lower nuclear charge
Boron
More occupied energy levels
or
Lower nuclear charge
Phosphorus
Zinc
Platinum
Iodine
Nitrogen
or
or
Arsenic
Nickel
or
or
or
Osmium
Periodic Trends
Page 38 of 62
We have now learned how to determine how big neutral atoms are. Similar logic can be applied if we
want to examine the radius of ions. Ionic radius is the distance between the nucleus of an ion and its
outermost electrons. Let’s begin our discussion by looking at what happens when a positive ion is
formed from a neutral atom.
Consider the neutral magnesium atom (left) and the positive ion that is formed when it loses two
electrons (right).
The neutral atom has a configuration of 1s22s22p63s2. The outermost electrons are in the third energy
level. However, the positive ion has a configuration of 1s22s22p6. The ion’s outermost electrons are
only in the second energy level. What happens to the size of the atom as it loses electrons to become a
positive ion?
In making the positive ion, the entire outer energy level is stripped away from the magnesium atom.
Therefore, positive ions have a smaller radius than their neutral counterparts due to the loss of
an energy level.
Periodic Trends
Page 39 of 62
In addition, it should be fairly obvious that a positive ion will be smaller than a neutral atom based on
the number of each subatomic particle present in the atom or ion. Consider the neutral neon atom
(below, left) and the positive magnesium ion (below, right). Neon atoms have 10 protons pulling in 10
tiny electrons. Magnesium ions are isoelectronic with neon atoms – that is, they have the same
number of electrons. The magnesium ions have the same 10 tiny electrons, but a nucleus containing 12
protons. Twelve is greater than ten, so the nuclear pull is stronger, and the magnesium ion is smaller.
A similar phenomenon occurs as electrons are added to neutral atoms to make negative ions. An atom
of nitrogen has 7 protons and 7 electrons. A nitride ion, N3−, has the same 7 protons, but 10 electrons.
The nucleus is incapable of pulling in the extra electrons, so the outermost electrons get further away
from the nucleus. As a result, the size increases.
Periodic Trends
Page 40 of 62
So, to sum up the trends for atomic and ionic radius:

Radius increases as you move down through the periodic table due to an increase in the amount of
occupied energy levels. Radius decreases as you move up due to the presence of less energy levels.

Radius decreases as you move to the right, due to increasing nuclear charge. It increases as you move
to the left, because of lessened nuclear pull.

A move up or down in the periodic table generally has a more dramatic effect on radius than
moving left or right. This is not an absolute rule, but can serve as a handy guideline if needed.

The radius of positive ions is smaller than that of their neutral counterparts. Atoms that form
positive ions often lose their entire outer energy level in making ions. What remains is much
smaller than the original uncharged atom.

The radius of negative ions is larger than that of their neutral counterparts. When an atom forms a
negative ion, it fills the outer energy level with extra electrons. The nucleus has a tough time
pulling in the additional electrons.
To review these concepts, we will play another card game. Andrew Miller’s Radius War is a card game
played between two players. It was devised by a former Lincoln Park student Andrew Miller (’14), and
is loosely based on the common card game, War.
To begin play, the players must first obtain a deck of Radius War cards from the instructor. Also, the
players will each need a periodic table for reference.
The Radius War card deck is divided evenly among the two players, giving each a face-down stack of
cards. In unison, each player reveals the top card of his/her deck – this is a “battle” – and the player
with the card that represents an atom or ion of greater size wins, taking both the cards played and
moving them to the bottom of his/her stack. Before the cards move, however, the players must discuss
why the winner has the atom or ion with greater radius. Phrases similar to the following should be
employed to guarantee understanding:
“Nitride ions are bigger than Oxygen atoms because Negative ions are always bigger than neutral atoms.”
“Carbon atoms are larger than Fluorine atoms because Carbon has a smaller nuclear charge.”
“Bromine atoms are bigger than Nitrogen atoms because Bromine has more energy levels.”
This step cannot be skipped. It is the point of the entire activity.
Periodic Trends
Page 41 of 62
If the two cards played are of equal value, then there is a “war.” Both players play the next two cards of
their piles face down and then another card face-up. The owner of the face-up card representing the
larger atom or ion wins the war and adds all of the cards in play to his/her stack. If the face-up cards
are equal, war continues, and the process is repeated.
If someone runs out of cards during Radius War, that person has lost the game. If there is no winner
after 15 minutes, play is stopped and the winner is the player who possesses the most cards at that
time.
When you are done playing the game, answer the following questions to demonstrate mastery.
Which one of the following series of atomic or ionic radii is NOT arranged in order of increasing size?
A.
B.
C.
D.
Li, Na, K
Na, Mg, Al
Cl−, Br−, I−
F−, O2−, N3−
Reasons:
Correct Answer: _____
Describe and explain the trend in atomic radius as you move right in the periodic table from Na to Cl.
On the right is a table containing some information about
the first six noble gases. What value would you predict
for the radius of Radon, the sixth noble gas? Why?
Periodic Trends
Atomic
Number
2
10
18
36
54
86
Element
Page 42 of 62
He
Ne
Ar
Kr
Xe
Rn
Atomic
Radius (Å)
0.93
1.12
1.54
1.69
1.90
?????
What is the order of decreasing radii for the species Cl, Cl1+, and Cl1−? Explain your answer.
Briefly explain why the magnesium ion is much smaller than the magnesium atom.
Briefly explain why there is a large increase in ionic radius from silicon to phosphorus.
Briefly explain why the ionic radius of Na1+ is less than that of F1−.
Periodic Trends
Page 43 of 62
The ionization energy is the minimum
energy required to remove an electron from a
neutral atom, in order to make a positive ion.
It is measured in joules. The ionization of
sodium is pictured on the right.
Consider the graph below, which contains the
ionization energy for the first 20 elements in
the periodic table. Consult a periodic table as
you view the graph.
What elements have the highest ionization energy? Why do you think that is?
What happens to ionization energy as we move to the right across a period in the periodic table?
Periodic Trends
Page 44 of 62
Consider the same graph. This time, line segments have been drawn connecting elements to other
elements in their families. What happens to ionization energy as we move down a group in the
periodic table?
How does the trend for ionization energy compare to the trend for atomic radius?
To sum up, ionization energy is the amount of energy needed to remove an electron from an atom in
order to create a positive ion. It is high at the top of the periodic table, where few energy levels are
occupied, and low at the bottom of the table when electrons are far away from the nucleus. It is high at
the right side of the table, when the effective nuclear charge is high, and low on the left side, when the
nuclear charge is low.
The trend for ionization energy is largely the exact opposite of the trend for size/radius.
Periodic Trends
Page 45 of 62
Circle the correct answers on the left. Circle the reason for the answer on the right. Read each question
carefully – some are about size/radius, and some are about ionization energy. Use your periodic table.
Which atom has a higher ionization energy?
Sodium
or
Chlorine
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
More occupied energy levels
or
Lower nuclear charge
Which atom has a lower ionization energy?
Aluminum
or
Phosphorus
Which atom has a larger radius?
Selenium
or
Oxygen
Which atom has a higher ionization energy?
Rubidium
or
Potassium
Which atom has a smaller radius?
Strontium
or
Iodine
Which atom has a higher ionization energy?
Bromine
or
Arsenic
More occupied energy levels
Which atom has a lower ionization energy?
Phosphorus
or
Arsenic
Which atom has a larger radius?
Calcium
or
Manganese
It is a little tricky to keep track of the patterns in the table when examining more than one trend at a
time. Therefore, it is crucial to go slowly through these problems, and make sure you fully understand
what is being asked before drawing any conclusions.
Periodic Trends
Page 46 of 62
Ionization energy is the energy required to remove an electron to turn a neutral atom into a positive
ion. Electron affinity is equal to the amount of energy that is released when a neutral atom takes in an
electron to become a negative ion. If it sounds like electron affinity and ionization energy are related,
that’s because they are. Electron affinity is essentially the opposite of ionization energy.
Ionization Energy:
𝑁𝑎
Electron Affinity:
𝐶𝑙 +
→
𝑁𝑎1+
𝑒−
→
+
𝑒−
𝐶𝑙1−
If we look at the magnitude of the energy associated with electron affinity, and not the sign, we can see
a trend similar to ionization energy. The electron affinity goes up as we move to the right across a
period in the periodic table. It goes down as we move to the bottom of a group.
For the purposes of this course, you should view electron affinity as a trend that is pretty much parallel
to ionization energy. Ionization energy is the amount of energy that needs to go into the system to
facilitate the removal of an electron. Electron affinity is the amount of energy that comes out of the
system when an electron is added. Both of these trends have to do with the nucleus’s ability to pull in
electrons, in doing so, making the atom smaller.
When ionic compounds are formed, one species loses electrons to become positive ions. Another gains
electrons to make negative ions. Ionization energy and electron affinity correspond with these two
processes, respectively.
Periodic Trends
Page 47 of 62
In covalent bonds, electrons are not transferred between atoms. They are instead shared between
them. The degree to which an atom holds onto shared bonding electrons is called electronegativity.
As you can see in the table below, electronegativity goes up as we move to the right in the periodic
table. It decreases as we move down a group. This exactly mirrors the trends for ionization energy and
electron affinity, and is exactly the opposite of the trend for size/radius.
Look at the chart above. From what you know, and from looking at the definition of electronegativity,
why do you think the Noble gases have been omitted from the chart?
The difference in electronegativities of elements involved in bonding does a lot to determine the nature
of the bond. Consider the bond between sodium and fluorine, and the bond between chlorine and
fluorine. What is the difference in electronegativity in each bond? How are the bonds different? Think
back to what you know about bonding, naming, and formula writing as you formulate your answer.
sodium and fluorine
Periodic Trends
chlorine and fluorine
Page 48 of 62
Dmitri Mendeleev's discovery of the Periodic Law ranks as one of the greatest achievements in the
history of science. It has survived the test of time and stands to this day as the single most important
tool to understand the chemistry of the elements. As we try to understand the essence of this
discovery, it is worthwhile to go back in time and look at how it was achieved.
In the years 1868-1870, Dmitri Mendeleev, a professor of chemistry at the University of St. Petersburg
in Russia, was writing a new textbook called Principles of Chemistry. More than 60 individual elements
were known, along with a great many facts about their properties and compounds. Mendeleev knew
the atomic masses of the elements, their densities, boiling points, and melting points, as well as the
formulas of their compounds with hydrogen, oxygen, and chlorine. What was missing was a way to
organize these facts, a way to understand how individual facts related to each other – in short, a way to
classify the elements. The following quote from Mendeleev reveals his thoughts at the time:
"I wished to establish some sort of system of elements in which their distribution is
not guided by chance ... but by some sort of definite and exact principle."
Mendeleev decided to arrange the elements according to their atomic mass. He wrote out the exact
atomic masses (as they were known at the time) in the margin of a list of the elements, then wrote out
separate cards for each of the elements, with their atomic mass and other chemical and physical
properties. Using these cards, Mendeleev played "chemical solitaire" for several hours, finally copying
to a sheet of paper the arrangement he had worked out with the cards. With slight modification, this
became Mendeleev's first Periodic Table of the Elements.
The purpose of this activity is to re-create Mendeleev's discovery of the classification of the elements
and the periodic law using a special deck of element cards. The real properties of the elements, but not
their names or symbols, are written on these cards. As the cards are arranged and rearranged based on
logical trends in some of these properties, the nature of the periodic law should reveal itself.
Define each property and give its typical units, if appropriate.
Ionization energy
Atomic radius
Atomic mass
Melting point
Periodic Trends
Page 49 of 62
Density
Electronegativity
1. Form a group with three other students. Obtain a
deck of element cards and spread the cards out on
the table.
2. Each card lists the properties of a single element
(X), as shown at the right:
*Density values are in units of g/cm3 for solids
and liquids, g/L for gases.
**Dashed lines for a property indicate that no
data is available. Some elements, for example,
may not form a compound with hydrogen.
3. Working together, discuss the possibilities for
arrangement of the element cards with all members
of the group, and look for a logical arrangement of
the cards. Consider the similarities and differences
among the elements as well as possible numerical
or logical trends in their properties.
Ionization
Energy
Atomic
Mass
Formula of its
-chloride XCla
Density*
Atomic
Radius
Formula of its
-oxide XbOc
Melting
Point
Formula of its
-hydride XHd**
Electronegativity
4. It is NOT within the rules of this game of chemical
solitaire to look up information in a textbook or to
use a modern periodic table as a guide!
Mendeleev's greatest insight in creating the periodic table was in recognizing there were some gaps when
the elements were arranged in logical order. He had the ingenuity not only to leave blanks in his table for
the missing elements, but also to predict their properties.
5. One of the element cards is also missing in your deck of cards. Decide where the missing element
belongs in the arrangement of the elements and rearrange the cards if necessary to accommodate
the missing element.
6. Below, fill in the Table of the Elements to illustrate a logical arrangement of the element cards. To
do this, write down only the atomic mass of each element, as shown on its card. Leave a blank
space for the missing element.
Periodic Trends
Page 50 of 62
7. Predict the properties of the missing element by averaging the properties of its nearest neighbors.
On the worksheet, complete the card for the missing element by entering its predicted properties
alongside the name of each property.
8. Answer Questions 1-7 on the following pages.
Table of the Elements
Properties of the Missing Element
Ionization
Energy
Atomic
Mass
Formula of its
-chloride XCla
Density*
Atomic
Radius
Formula of its
-oxide XbOc
Melting
Point
Formula of its
-hydride XHd
Electronegativity
Periodic Trends
Page 51 of 62
1. Mendeleev's Periodic Law can be stated: "The physical and chemical properties of elements are
periodic functions of their atomic masses". Looking at your arrangement of the element cards,
describe in your own words what the term "periodic function" means.
2. Some of the properties listed on each card are periodic properties, others are not. Name one
property that is periodic and one that is not.
Periodic Property: ____________________ Non-periodic Property: ____________________
3. The elements in the modern periodic table are arranged in order of increasing atomic number
(instead of increasing atomic mass). Why didn't Mendeleev use atomic number to arrange the
elements?
4. From your instructor, obtain a handout showing one possible arrangement of the element cards.
Identify each element on the handout with its atomic number and chemical symbol. Use your
textbook to obtain this information.
Periodic Trends
Page 52 of 62
Ionization Energy
5. Using the possible arrangement of the element cards obtained from your instructor, plot the values
of ionization energy in the graph below. You will have to come up with your own y-axis values.
Atomic Number
6. There are certain trends in the properties of the elements, both within a column (from top to
bottom) and across a row (from left to right) in the periodic table. On the arrow for each property,
write the word increases or decreases to describe how that property changes.
Periodic Trends
Page 53 of 62
7. On the outline of the periodic table shown below, locate and label the metals and nonmetals. Use
your textbook to define these terms, if necessary.
So far, we have considered a number of periodic trends that exist among the elements. First, we looked
at atomic radius and ionic radius, which explored how far electrons can position themselves from the
nucleus. Then, we considered ionization energy, electron affinity, and electronegativity, which are all
related to the amount of pull a nucleus has on its electrons. Size and “pull” are in a delicate balance in
every atom.
How many protons does lithium have? _______
How many protons does cesium have? _______
If the nuclear charge of cesium is so much greater than that of lithium, why isn’t the size of the cesium
atom much smaller than that of lithium?
The answer lies in another periodic trend, the trend
related to shielding. Shielding is the collective action
of all the inner electrons to repel the outer electrons
and weaken the attraction between the protons and
the outermost electrons. Shielding increases as you
move down the periodic table. Shielding does not
change as you move from left to right. Shielding
increases as you move down because a downward
move is associated with an increased number of energy
levels between the nucleus and the outer electrons. A
left/right move has no such increase in shells.
Periodic Trends
Page 54 of 62
Other vocabulary that might occur when dealing with periodic trends include the following:
Nuclear charge is the amount of positive charge exerted by the nucleus. Nuclear charge increases with
the addition of more protons. Therefore, nuclear charge increases as atomic number increases.
Metallic character is the degree to which an atom behaves as a metal. Metals lose electrons to form
positive ions, and are malleable and ductile when in their elemental form. Metallic character
increases as you move down and to the left, just as atomic size does.
Nonmetallic character is the degree to which an atom behaves as a nonmetal. Nonmetals gain electrons
to form negative ions, and are brittle when in their elemental form. Nonmetallic character increases
as you move right and up, just as ionization energy, electronegativity, and electron affinity do.
More will be made of these last two trends as we further explore bonding between atoms. For now, it is
important that you master the periodic trends atomic radius, ionic radius, ionization energy, electron
affinity, electronegativity, and shielding.
Periodic Trends
Page 55 of 62
Completely answer all questions on the following pages.
Restate in one or two words: “The amount of energy required to remove one electron from the outer
shell of a neutral atom.”
Restate in one or two words: “The tendency of an atom to hold on to its shared electrons while engaged
in a chemical bond.”
Restate in one or two words: “The actions of the inner electrons, diluting the force of the attraction
between nucleus and outermost electrons.”
Which has greater shielding, Au or Cu? Why?
Which is larger in size, Au or Cu? Why?
Which has greater ionization energy, Cu or Ag? Why?
Which has greater shielding, Xe or Ar? Why?
Which is larger, Ca or Cs? Why?
Periodic Trends
Page 56 of 62
Which has greater shielding, Se or Ra? Why?
Which has greater nuclear charge, Zn or Se? Why?
Which is larger, Mg or P? Why?
Which has greater ionization energy, Fe or K? Why?
Restate in one or two words: “Half the distance between the nuclei of two like atoms.”
Which has greater ionization energy, Cl or Al? Why?
Which has greater shielding, P or Ar or neither? Why?
Which is larger, Os or Fe? Why?
Periodic Trends
Page 57 of 62
Using a spreadsheet, follow the directions given below and plot the following information.
Atomic
Number
Element
Ionization
Potential
(eV)
Atomic
Radius
(Å)
Atomic
Number
Element
Ionization
Potential
(eV)
Atomic
Radius
(Å)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
H
He
Li
Be
B
C
N
O
F
Ne
Na
Mg
Al
Si
P
S
Cl
Ar
K
Ca
Sc
Ti
V
Cr
Mn
Fe
Co
13.60
24.59
5.39
9.32
8.30
11.26
14.53
13.62
17.42
21.56
5.14
7.65
5.99
8.15
10.49
10.36
12.97
15.76
4.34
6.11
6.54
6.82
6.74
6.77
7.44
7.87
7.86
0.30
0.93
1.52
0.89
0.88
0.77
0.70
0.66
0.64
1.12
1.86
1.60
1.43
1.17
1.10
1.04
0.99
1.54
2.31
1.97
1.60
1.46
1.31
1.25
1.29
1.26
1.25
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Ni
Cu
Zn
Ca
Ge
As
Se
Br
Kr
Rb
Sr
Y
Zr
Nb
Mo
Tc
Ru
Rh
Pd
Ag
Cd
In
Sn
Sb
Te
I
Xe
7.64
7.73
9.39
6.00
7.90
9.81
9.75
11.81
14.00
4.18
5.70
6.38
6.84
6.88
7.10
7.28
7.37
7.46
8.34
7.58
8.99
5.79
7.34
8.64
9.01
10.45
12.13
1.24
1.28
1.33
1.22
1.22
1.21
1.17
1.14
1.69
2.44
2.15
1.80
1.57
1.41
1.36
1.30
1.33
1.34
1.38
1.44
1.49
1.62
1.40
1.41
1.37
1.33
1.90
1. Using a spreadsheet, graph the ionization potential (y-coordinate) versus atomic number
(x-coordinate) for elements 1-54. Make sure to properly label the graph.
2. Using a spreadsheet, graph the atomic radius versus the atomic number for elements 1-54. Label
the graph.
3. What do the units “eV” and “Å” stand for?
eV =
Å =
Periodic Trends
Page 58 of 62
On the blank Periodic Chart below, clearly locate the following, using a color code:
a.
b.
c.
d.
e.
f.
g.
h.
i.
Representative elements
Transition elements
Metallic elements
Nonmetallic elements
Metalloids
Alkali metals
Alkaline-earth metals
Halogens
Noble gases
On the same periodic chart, locate these elements and write in their atomic symbols:
a.
b.
c.
d.
e.
sodium
potassium
chlorine
nickel
bromine
f. phosphorus
g. carbon
h. magnesium
i. sulfur
j. calcium
Periodic Trends
k. barium
l. aluminum
m. silicon
n. zinc
o. lead
Page 59 of 62
Notice that the graph of first ionization potential versus atomic number consists of generally rising
values followed by sharp drops. List the elements on the five major peaks in this graph. What name is
given to this group of elements?
List four elements located at the bottom of the sharp drops. What name is given to this group of
elements?
Assuming that the periodic trends indicated on the graph continue, what value do you predict for the
first ionization potential of cesium, Cs, atomic number 55?
What generalization can be made about the change in first ionization potential as the atomic number
increases in a period (such as Na to Ar)?
What generalization can be made about the change in first ionization potential as the atomic number
increases in a group (family)?
Looking at the atomic radius versus atomic number, what would you predict for the atomic radius of Cs,
atomic number 55? (Use Cl-Ar-K and Br-Kr-Rb as examples.)
Periodic Trends
Page 60 of 62