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Topic 3 Atoms
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Topic 3- A Sections
2.1 The Atomic Theory
2.2 Discovery of Atomic structure
2.3 Modern view of atomic structure
2.4 Atomic weights
2.5 periodic table
Focus questions:
• If an atom is too small to be seen how do
we know it exists?
• How do we know about the atom’s
structure?
• What does an atom look like?
To consider:
Suppose you were to break a piece of chalk in half.
…then in half again. …and again.
How many times could you continue break it in half?
To consider:
Your piece would go from one-half, to one quarter.
…to 1/8th , 1/16th , etc.
…and could never to zero.
To consider:
Or is there a point…
…where the process would have to stop?
When you reach a single particle of chalk.
To consider:
…this is the concept of the atom.
History of atomic theory
2 views (theories) of matter:
Continuous: matter broken down indefinitely
Ex: how many times can a piece of chalk be divided?
Indefinitely? Or will we reach a basic particle?
Discontinuous: matter breaks down into a simple building block
Democritus (400BC)–was an ancient Greek philosopher
Coined the term “atomos” meaning indivisible
His was the Philosophical atom
– as no evidence was examined
Philosophers like to think about things that
usually can’t be experimented on, so they don’t
look for evidence.
Hey, sometimes
you gotta make
this stuff up.
Link

2.1 The Atomic Theory
But if no one’s ever seen an atom, how do we know it exists?
It’s a “theory”
Theory: a mental picture (a concept)
created to help understand an
observed phenomenon
Realize: since theories are mental creations,
they aren’t real and can’t be “proven”. We can
however find evidence to support them and use
them to identify new relationships and make
predictions.
Laws state an observed regularity but without
explanation. Example: “objects with mass are
attracted to each other “ is the law of gravity.
Why? No one really knows, but there are theories!
John Dalton (1807) ultimate particle model
1. All matter made of ultimate particles (called atoms) that are extremely small
2. Atoms of a given element are identical, while different elements have different relative weights
ex: Nitrogen atoms are 14 x heavier than Hydrogen atoms (the lightest atom)
so we will say that H = 1, while N = 14
3. Atoms of elements cannot change into different elements nor can they be created or
destroyed during reactions.
4. Compounds are formed by combining atoms of different elements in
unique combinations. A chemical reaction is the rearrangement of atoms
into new arrangements forming new compounds
 link
Dalton took evidence from various laws; and the atomic theory provides an explanation for them….
Law of conservation of mass (mass is never lost or gained during reactions)
Why? Because atoms can’t be created or destroyed, just rearranged
Law of constant composition (compounds always have the same proportions of elements in them)
Aka law of definite composition, law of definite proportions
Why? A specific arrangement of atoms is required to make a given compound
Dalton was also
one of the first
to use
symbolism to
represent
atoms,
elements, and
compounds…
Dalton bio
16 X
+
8Y
8 X2Y
Mass of 16 x + mass of 8 Y is still the same when rearranged into the 8 molecules of X 2Y
2.1
Link
Dalton predicted the law of multiple
proportions:
Example: two compounds of Carbon and oxygen:
When carbon is only partially burned it forms a
gaseous product.
…When carbon is completely burned it also
forms a gaseous product.
The mass of oxygen in the product from
complete combustion is exactly twice the
oxygen in the partial product. Why?
For example; for every 10 grams of
carbon there are 26 grams of oxygen
in the complete product.
Whereas for every 10 grams of carbon in
the partial product there are only 13 grams
of oxygen.
Can you use the atomic theory to explain this?
If your theory is correct it you
should be able to see it at work
in different ways!
The two gases are
carbon monoxide
and carbon dioxide
So, if you compare two different
compounds made of the same
elements, there must be a simple
ratio between the two compounds,
for a given element.
If your theory is correct it you
should be able to see it at work
in different ways!
The theory tells us that there must be exactly
twice as much oxygen in carbon dioxide as
carbon monoxide since there are twice as
many atoms in one compared to the other
Think about it…You can’t see the atoms to
count them. So…
It’s the only valid explanation!
The idea (theory) of the atom…
explains why chemicals exhibit multiple proportions (the law)
Try one: Water is always 11.1% hydrogen and 88.9% oxygen (by weight)
Hydrogen peroxide is 5.89% hydrogen, and 94.1% oxygen.
This means that in 100 gram samples of those two compounds there
is 11.1 grams of hydrogen and 88.9 grams of oxygen
and 5.89 grams of hydrogen, and 94.1 grams of oxygen; respectively
Show mathematically, how these two compounds illustrate the law of multiple
proportions:
To do this, calculate the simple whole number difference for oxygen in the two
compounds, for a fixed quantity of hydrogen
(or fix the oxygen, then compare the hydrogen, you’ll see that it doesn’t matter)
Need a hint?
Calculate the grams of oxygen per 1 gram of hydrogen for each.
divide the mass of O by the mass of H for each
For water, 89.9 grams H = 8 g O per g H
11.1 grams O
For hydrogen peroxide, 94.1 grams H = 16 g O per g H
5.89 grams O
See the ratio?
8:16 = 1:2
Twice as much O in peroxide!
Use the atomic theory to explain the difference:
If water is H2O, than peroxide can be H2O2?
2.2 Discovery of atomic structure
Thomson electron discovery link
This Thomson guy looks like a
serious character, eh?
Electron
JJ Thomson (1897) did experiments with the cathode ray tube or “CRT”
High voltage applied to the electrodes caused streams of particles from the negative “cathode”
Found that Particles were emitted by any substance tested, and were smaller than any known atom
(were subatomic)
Where did they come from? What were they?
Thomson deduced that they must come
from inside the atoms and be part
common to all atoms. First called
cathode rays, become known as
electrons.
Shadow created by Maltese cross
blocking cathode rays
Older TVs and computer
monitors are CRTs
TV, computer
monitor
Cathode Ray Tube
Cathode (-)
Anode (+)
How do we know that the cathode rays
travel from the cathode to anode?
2.2
How can the size of the mass of the electron by measured?
In another experiment, Thomson calculated the charge to mass ratio.
By finding the magnetic force (controlling gravities pull on the mass) that canceled out the
electric field force (controlling the pull and push on the electrical charges) he found their
ratio as 1.76 x 108 coulombs per gram.
As a result, if either the charge or mass of the electron could be found, then the other could be
calculated from this ratio.
(that’s up next!)
In 1907, Robert Millikan, designed an experiment whereby he sprayed oil droplets into a chamber
allowing a few to drop and gain excess electron charge with x-rays. He adjusted the electrical
field charge until the drops were suspended in mid air between the plates.
Because each drop had gained a different
number of electrons, each drop took
a different force to keep it suspended.
Millikan knew that all the required charges
were a simple multiple of the charge on
just one electron. By finding this common
factor, he was finding the charge on just
one electron.
For example, what if Millikan had found these
values for charge:
-4.8 x 10-19 Coulombs
-3.2 x 10-19 Coulombs
-6.4 x 10-19 Coulombs
What value would he have concluded is the common factor,
I.e.. What value is the charge on just one electron?
Notice:
all are multiples of -1.6 x 10-19 Coulombs
This is the charge on a single electron
It is slightly more complex than this but you get
the idea? Click here to see a flash video clip
for more explanation
Millikan’s oil drop experiment link
Now….Remember the charge to mass ratio:
1.76 x 108 coulombs per gram?
-1.60 x 10-19 C
=
1.76 x 108 C/gram
9.10 x 10-28 grams
mass of an electron
J.J. Thomson’s plum pudding model of the atom
Thomson reasoned that these tiny electrons were
imbedded in a positive atom.
This model didn’t last too long!
Radioactivity
In the Late 1800’s Discovery of Uranium, Polonium, and Radium
samples emitting high energy “radio-activity” of three types:
 Alpha radiation (+2 charge, with large mass)
 Beta particles radiation (-1, similar to cathode ray electrons)
 Gamma radiation (no charge or measurable mass)
Separation
of particles
between
charged
plates
link
Studies by French scientists
Henri Becquerel along with
his students Pierre and Marie
Curie provided further
evidence for the existence of
subatomic particles
Link
Both
Curies
died likely
due to
their
exposure
to
radiation
Discovery of the Nucleus:
Rutherford Gold foil Experiment
British scientist Ernest
Rutherford experimented
with Alpha radiation.
He Shot alpha (+) particles at
a piece of thin gold foil.
The Results: Most alpha
particles passed undeflected
(as expected of radiation)
Some alphas were slightly
deflected from original
path (not unexpected)
A Few were significantly
deflected.(unexpected)
Link
What Rutherford expected
(based on thomson’s plum
pudding model)
The atom is mostly empty space
with a tiny dense positive nucleus
containing almost all of the mass.
Electrons revolve rapidly around
outside the nucleus, like planets
orbiting the sun.
What Actually Happened
(alphas +, were deflected by the
positive nucleus)
Rutherford’s Model of the Atom
Empty space
(with a few tiny
Electrons circling!)
If the atomic radius ~ 100 pm = 1 x 10-10 m
The nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m
“If the atom is the Houston Astrodome, then the nucleus is a marble on the 50-yard line.”
Video
Link
2.2
Proton was discovered by Rutherford in 1919.
Recognized as a Hydrogen nucleus (single proton) given off as radiation.
Interpreted as other elements must be made of hydrogen nuclei-protons.
Proton mass = 1.67 x 10-24 g
Neutron: James Chadwick (1932)
Rutherford’s Dilemma:
Hydrogen atoms have 1 proton and mass = 1 atomic mass unit
Helium atoms have 2 protons, but mass = 4 atomic mass units
So, where does the extra mass come from?
There must be additional particles in atoms that add mass but without charge
 + 9Be
1n
+ 12C + energy
This is a nuclear equation. We will study these later in the year.
In 1932 Chadwick bombarded Beryllium atoms with alpha particles and discovered neutron radiation
Neutron mass = 1.67 x 10-24 g
Same as a proton
Check your understanding:
1.
Which model of the atom was the simplest? What were its
characteristics?
Dalton’s, solid spheres with different masses
2. How did Thomson surmise that electrons were subatomic
particles? How did he know they were negatively charged?
Smaller than the smallest atom, attracted by positive charge
3. Why did most of the alpha particles pass through the gold foil
undeflected? Why did a few get deflected?
Atoms are mostly empty space, but have a small positive nucleus
4. Why can’t two atoms pass through one another if there’s so
much empty space?
Hint: what do negative electrons (like charges)
do when near each other?
They repel each other like a force field!
Regents level questions
2.3 The modern view of atomic structure
Video link
The Charge cloud model: Nucleus containing Protons and neutrons
Electrons circling rapidly around outside nucleus would appear as a cloud
Protons Note: AMU = atomic mass unit
Mass = 1.67262 x 10-24 g
atoms
so tiny, the gram is not a very convenient unit to
-19 coulombs
Charge =Since
+ 1.602
x 10are
use to represent their mass.
aka: +1 charge
NeutronsSince it turns out that protons and neutrons are very close in mass,
-24
Mass = 1.67493
x 10
a new unit
wasgdeveloped called the atomic mass unit. Essentially,
Neutral charge
the mass of a proton or neutron is assigned a mass of one amu, or
simply 1 u.
Since protons and neutrons are so close in mass, we
assign them both a mass of 1 atomic mass unit (1 u)
As you will see, to find the mass of an atom you will need only add
Atomic size: most atoms 1 to 5
Electronsup the mass of the number of protons and neutrons. (electrons, as it
angstroms in diameter
Mass = 9.10939
10-28 g
= negligible
mass
turns outx have
almost
no mass)
(1 Å = 10-10 meters)
compared with Protons and neutrons ( 0 amu’s)
-19 coulombs
here
if you
want more
detail
on this idea
Charge =Click
- 1.602
x 10
aka
-1 charge
10,000,000,000 atoms lined up
would only form a line 1 mm long!
*(For convenience, atomic mass units are used (u):
1 u = 1.66054 x 10-24 g
Amu’s are much easier to work with than grams!
AP
(b) Hint: calculate atoms per line
X 10 +2
1.54 Å x 10-10 m x 1 pm
1Å
10-12 m -2
1 atom x 1 Å
x 10-3 m x 0.20 mm
1.54 Å
10-10 m
1 mm
1 line
Atomic number, mass number, and isotopes
Elements get their properties from the number of protons.
Number of protons in nucleus is called the Atomic number (the “Z” number)
The mass of an atom comes from its protons plus its neutrons (electron weight is negligible)
The Mass number (“A” number) = number of protons + number of neutrons
= atomic number (Z) + number of neutrons
The neutrons are calculated by A# minus Z#
Symbolism:
Mass Number
(superscript)
Atomic Number
A
ZX
Tutorial link
Element Symbol
(subscript)
Ex: The most common form of carbon (atomic #6) has 6 protons and 6 neutrons
6 protons + 6 neutrons
6 protons
Carbon –12
has 12 – 6
= 6 neutrons
This is an isotope of carbon.
It has 6 protons, but 8 neutrons.
6 + 8 = 14 mass
Carbon –14 is radioactive (its nucleus is not stable)
It is used to estimate the age of fossils, remember?
Isotopes are atoms of the same element (X) with
different numbers of neutrons in their nuclei.
They have the same Z number (protons) but their A
number (mass) is different
Isotopes are identified by their masses:
C-12 vs. C-14
The three isotopes of hydrogen
Most hydrogen is H-1 (protium)
Tutorial link
Isotopes of an element have
the same chemical properties
and most samples of
elements have at least a
couple of different isotopes in
them. You have radioactive
carbon-14 in you!
Do You Understand Isotopes?
How many protons, neutrons, and electrons are
14
in 6 C ?
6 protons, 8 (14 - 6) neutrons, 6 electrons
How many protons, neutrons, and electrons are
11
in 6 C ?
6 protons, 5 (11 - 6) neutrons, 6 electrons
2.3
Check your understanding
An atom has 14 protons and 20 neutrons.
A. Its atomic number is
1) 14
2) 16
3) 34
B. Its mass number is
1) 14
2) 16
C. The element is
1) Si
D.
3) 34
2) Ca
3) Se
Another isotope of this element is
1) 34X
2) 34X
3) 36X
16
14
14
AP
AP
The four basic forces of matter
Gravity is the attraction
between the mass in
different objects
The nuclear strong
force overcomes
the repulsion of
protons packed
together in the
nucleus and holds it
together
In chemistry we deal mostly with
electrostatic forces since they
are responsible for the bonding
between atoms that hold
molecules together
Electrostatic or
electromagnetic
Click here for a Bill Nye link
Forces are between
charged objects like
electrons and
protons
(remember
opposite charges
attract, but like
charges repel)
The nuclear weak
force is used to
explain radioactive
emissions.
2.4 Atomic weights Tutor link
Elements in nature are mixtures of different isotopes.
The atomic weights listed on the periodic table are
averages of the different isotopes for an element
Ex: Naturally occurring carbon is a mixture of
three isotopes: Carbon 12, carbon 13 and
an insignificant amount of carbon 14
The atomic weight for carbon listed on
the periodic table is 12.0107
Sum of
To calculate this value:
Atomic weight =
Notice that the atomic
weight always
comes close to
isotope of greatest
abundance.
[(isotope mass) x (percentage abundance)]
= (12.000 u )(0.9893) + (13.00335)(0.0107)
= (11.8716) + (0.1391)
= 12.0107 amu
This is called
“weighted averaging”
The small amount of carbon 13 skews the mass to just above 12
Weighted averaging:
here is a simpler example:
Suppose you have three components to your grades:
Labs, Tests, and homework.
The weighting is Labs 25%, Tests 50%, and homework 25%
Your grades are 90% on labs, 75% tests, and 87% Homework
By adding up the product of the weight x grade you arrive at
and overall average of 81.75 or 82 rounded
Notice that this is closer to the test grade average since it
carries the highest weight?
In chemistry we are interested in the atomic weight average
Obviously, most chromium atoms have masses
less than 52.94, like maybe 51.94? A small
fraction of Cr – 53 atoms (52.94) will skew
the average mass up to 51.99!
(92.23%)(27.97693) + (4.68%)(28.97649) + (3.09%)(29.97377)
The mass spectrometer: measuring mass and abundance of isotopes
1) A sample
of a gas enters
and is ionized.
2) Ions accelerate
and bend as they
pass through a
magnetic field
Video link
Chlorine’s atomic mass (average) is 35.5
According to the graph is that reasonable?
3) Lighter atoms bend
more, heavier
bend less
4) Detectors separate
isotopes by mass
and the relative
signal intensity give
the % abundance
Information from the periodic table
Much of the data related to atomic
structure that you will need to solve
problems in chemistry can be found
on your periodic table
Regents level questions:
Electrons have equal
but opposite charge
from a proton but are
only a fraction as large
The nucleus contains
protons and neutrons
(making it always
positive in charge.
Electrons are in
orbitals outside the
nucleus
Positve is attracted to
negative. Alphas are
large particles with an
overall charge of +2
The charge of the
nucleus is the origin of
all properties in the
nucleus. That charge
is determined by the
number of positive
protons.
Atomic number 7
means +7 charge in its
nucleus
Atomic number 11
means its nucleus has
a +11 charge
15 protons has a +15
nuclear charge making
its atomic number 15 phosphorus
The lower value in the
symbol is the atomic
number – the number
of protons.
The lower number 11 –
the atomic number
identifies this as Na
The additional mass in
an isotope like C14
must come from extra
neutrons since both
must have the same
proton # - 6
Protons and neutrons
are the only massive
particles each
weighing 1 amu. 21 P
+ 24N = 45 amu.
Carbon is atomic number 6 = 6
protons; and 6 electrons to
make it neutral. A mass of 14
means there are an additional 8
neutrons of mass in the
nucleus.
The presence of different
isotope mass forms for each
and every element means
they must be averaged to find
the overall atomic mass
Calculate, but if 75% has a
mass of 35 vs. only 25% is
37, the mass should be
closer to 35 than 37
Weighted averaging
2.5 The Periodic Table
Link

Dmitri Mendeleev (1834 - 1907)
Dmitri Mendeleev was a Russian chemist, who, in 1870, looked for a way to organize the
elements. He wrote the known properties of elements on blank playing cards.
Explosive gas
1
H
He placed element cards in order of increasing mass
and looked for patterns.
Inert gas
4
Notice the formulas of the compounds formed with F and O.
He
HF H2O
Active metal
7
Li
LiF Li2O
Active metal
9
semimetal
11
Be
B
BeF2 BeO
BF3 B2O3
nonmetal
12
unreactive gas
14
Explosive gas
16
active gas
18
Inert gas
20
C
N
O
F
Ne
CF4 CO2
NF3 N2O3
OF2 O2
F2 F2O
Active metal
23
Active metal
24
metal
27
semimetal
28
nonmetal
31
nonmetal
32
Active gas
35
Inert gas
40
Na
Mg
Al
Si
P
S
Cl
Ar
MgF2 MgO
AlF3 Al2O3
SiF4 SiO2
PF3 P2O3
SF2 SO
ClF Cl2O
NaF Na2O
Active metal
39
After fluorine, he noticed that sodium was similar to lithium, and the pattern repeated.
K
After chlorine, he noticed that potassium was similar to sodium, etc.
KF K2O
Hydrogen starts the table since it’s the smallest, and the noble gases, once
discovered took their place at the end of the line.
TED
Link
Notice how elements line up into columns with similar properties?
Also, notice how the properties repeat each row?
That’s “periodic”!
If we add in the transitional elements in the middle
and the rare earth elements below, the present
table becomes recognizable
Click for
the element song
(Tom Lehrer’s original)
or
Daniel
Radcliffe
Sings
(cute clip)
Mendeleev’s Table
Was Organized first based on increasing mass
(but he allowed elements to group by similar properties)
Found properties of elements repeated periodically
(in a regular pattern)
Put elements in groups with similar properties
Key: Left spaces for elements that weren’t yet discovered
Eka-silicon - aka germanium
Properties repeat!
Mass dilemma:
mass sometimes
decreases
Henry Moseley (1913) Did X-ray studies
Periodic Law: “Properties of the elements are periodic
functions of their atomic numbers”
(nuclear charge, # protons)
Organized into groups (vertical columns) of elements with
similar properties
Organized into periods (horizontal rows) – properties
change systematically from metals to nonmetals to inert
(unreactive) gases
Group 1
Period 1
Period 2
Period 3
Etc.
Properties are
similar 
in columns
Group 2
Etc.
Properties change
systematically 
Left to right
The periodic table can be broadly divided into two categories:
Nonmetals
Metals: left side of the table
are shiny, malleable
elements, which have
difficulty holding onto
electrons during chemical
reactions – that is they are
chemically “weak”
In my classes I refer to
them as “losers”
Metals
Nonmetals: right side of
table are dull, brittle
elements which are
chemically strong, holding
onto their own electrons
and gaining electrons
during chemical reactions
In my classes I refer to
them as “gainers”
Notice: Two ways to distinguish groups:
Groups 1-18 or 1A to 8A and 3B to 10B
In Regents Chem we use 1 to 18, AP is 1A through 8A with group B in the middle.
The periodic table can be broadly divided into two categories:
Metals
Noble Gases
Nonmetals
The last column is
a group of
nonmetal
elements which
are so strong that
they are stable
and unreactive:
The Noble Gases
Hydrogen is the smallest so it starts the table, but its actually a
nonmetal so it is sometimes also shown here:
To Repeat: Hydrogen sits on the metal side,
but it’s actually a NONMETAL
H
Nonmetals
Metals
Si
Ge As
Sb Te
Po
Between the losers and
gainers, the metals and
nonmetals – along the border
between them sits the
metaloids: These elements
have properties of both metals
and nonmetals, depending on
the situation
Noble Gases
B
H
H
Nonmetals
Metals
Si
Ge As
Sb Te
In the middle of the table are
the transition metals
At the bottom are the rare earth metals
These extra metals arise due to the way in which electrons
arrange themselves in the atom. We will visit them in just a bit.
Periodic table organization – for extra help click here
Po
Noble Gases
B
H
Types of elements
Metals
Nonmetals
Metalloids
Solids
(one
liquid)
Solids and
gases
(one liquid)
Solids
Shiny
Luster
Malleable
Ductile
Good
conductors
of Heat
and
electricity
Noble gases
Gases
Dull
Luster
Brittle
Poor
conductors
Good
insulators
Semiconductors
Properties
of
both M & NM
Inert
or
Unreactive
Finding information on the table
Periodic table squares usually give the
basic information, but not always in the
same positions.
Some
tables give
lots of
information
but you
have to
look at the
key to
figure it out.
Memorize the positions of the required
elements on the periodic table
Click a square below to play the element
drag and drop game!
Easy
All elements
Try to associate the elements with their type (metals, nonmetals, noble gase, etc.)
and if possible, their group numbers. This will get you close. Don’t get discouraged.
As you practice you’ll start to get a sense for where things are. This will help you
figure stuff out when you don’t have a periodic table to look at (like on the AP test!)
Knowing the position of the elements on the table tells a lot of information.
Learning check:
1.
State the modern periodic law: “Properties of elements are….
“Periodic functions of their atomic number”
2. What are “groups” on the periodic table? How are the members
related to one another?
Vertical columns, have similar properties
3. What are the periods on the periodic table?
how do the properties change across a period?
Horizontal rows: change from metals to inert gases
4. What are the 3 + 1 types of elements?
Where is each located on the table?
How do their properties differ?
Metals on left are shiny, malleable, conductors:
noble gases on right are inert gases
nonmetals at the top right above the step are dull, brittle nonconductors:
, metalloids along the step have properties of both metals and nonmetals
Group 1 and 2 (S block)
alkali metals and alkaline earth metals
Both groups very reactive
Found in nature only in
compounds
Obtained from breakdown of
salts
Transitional metals
Group 3 to 12
Less reactive than s-block(group
1 and 2) metals
Generally similar properties
Many form colored ions
Some found in elemental state in
nature (ex Au)
Transition from group 2 to
group 13
Includes rare earth metals and
actinides of the f block.
Found in certain rare
minerals
Rare Earth metals
and actinides
Group 13 to 16
Nonmetals
Nonmetals above
Includes nonmetals of the
pnictogens (Nitrogen family)
chalcogens (oxygen family)
and halogens (fluorine family)
“Poor” Metals below
Softer metals with low
melting points
Semimetals in between
Poor metals
semimetals
Metalloids (semimetals )
• Along stepped line
• B, Si, Ge, As, Sb,
Te, Po
• Properties of both
metals and
nonmetals
• Ex: computer
“semiconductors”
made of silicon
Group 17 Halogens (salt-makers)
• Highly reactive
nonmetals
• Found in nature only
in compounds
• F gas - most active
nonmetal (reactive)
• Gas to liquid to solid
due to increasing
inter-molecular
(sticky) forces
Group 18 Noble gases
“Neon” signs
Very unreactive because
they have full electron
shells
Learning check:
1.
What families of elements are so reactive that they are only found in
nature combined in compounds?
Alkali metals – group 1 and halogens group 17
2. Where are the transitional elements located?
What kind of elements are they? Other traits?
Middle of table, relatively inactive, colored solutions
3. Which groups on the table contain both metals and nonmetals? Explain
Groups 13-16, nonmetals above line, metals below
4. Which halogen is most reactive?
Fluorine
What trend occurs in melting and boiling points for elements in group
17? Why does this trend occur?
MP and Bp increase, molecules get stickier as they get larger
5. List the 7 semimetals (metalloids):
Why are they named as such?
B, Si, P As, Se, Te, Po – properties of both metals and nonmetals
6. What elements exist as diatomic molecules when in their pure,
uncombined state?
BrINClHOF’s
Regents level questions
It the periodic law
Periods are horizontal,
groups vertical
20 protons is atomic number
20 – calcium, a group 2
element.
That’s what they’re called.
Same group (column)
Left, middle and bottom are
all metals. We’ll see why
later in the year.
Metals are conductors
Metals are malleable.
Left side of table
Si is a metalloid
Group 1 elements
That’s what they’re called.
Middle of the table,
groups 3 - 11
Calculate, but if 75% has a
transition elements like Cr
can have bright colors. Cr
produces yellow- orange
ions.
Only two liquids at STP. Hg
and Br.
That’s where they are.