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Elements are the
building blocks of
matter.
Chapter 2
S
In this chapter we will be
covering…
S ELEMENTS!!!
S The Periodic Table
and Chemical
Properties!!!
S The Periodic
Table and Atomic
Theory!
What is an Element?

An element is a pure substance that cannot be broken down
or separated into simpler substances.
 Each element is made up of only one kind of atom.

There are just over 100 different kinds of elements.

Elements are the same everywhere.

Iron (Fe) atoms found on Earth are
identical to iron atoms found on
meteorites, and on Mars.
Chemical Symbols

Different countries around the world have different national languages in which the
elements have different names

To make for clearer communication, an international set of chemical symbols are used.

Chemical symbols have either 1 or 2 letters, the first is
always capitalized.
In many cases, the symbols are derived from ancient Greek names:
Name
Chemical Symbol
Greek Name
Origin of Elements Symbol

Oxygen
O
Oxys Genes
(acid forming)

Hydrogen
H
Hydros Genes
(water forming)

Chlorine
Cl
Chloros
(pale green)

Potassium
K
Kalium
(latin for potash)

Magnesium
Mg
Magnesia alba
(a place in Greece)

Iron
Fe
Ferrum
(latin for iron)
Chapter 2.2
Periodic Table and Chemical Properties
S
Introducing the Periodic Table of Elements!

Chemical Symbols are used to represent elements in the periodic table.

These are arranged by their chemical and physical properties.
p. 54
Vocabulary Words



Atomic Mass - mass of average atom (why decimals?)
Atomic Number - number of protons (atoms, by definition,
are neutral-no charge; therefore, atomic number is also equal
to the number of electrons)
** Atomic number defines the element**
Ionic Charge - electric charge that forms when an atom gains
or loses electrons
When an atom gains a charge it is then called an ion

Reading the elements on the PT
Periodic Table is all about the
patterns
S one such pattern is that the periodic table is arranged in
rows of increasing order of atomic number (that is,
number of protons)
Patterns continued...
S a second set of patterns separate the elements into:
1. Metals
2. Non-metals
3. Metalloids
Metals

Metals: elements that are typically hard, shiny, malleable, ductile,
and good conductors of heat and electricity.
Mn
Non-Metals


Non-Metals: elements that are typically not shiny, malleable, or
ductile and are poor conductors of heat and electricity.
Usually gases or brittle solids at room temperature.
P
Br
I
Metalloid

Metalloids: elements that share some properties with metals and
some properties with non-metals
Ge
Si
Comparison Chart
Patterns continued...
S Another pattern.....
S Horizontal rows
S Called periods
The Periodic Table...PERIOD.
1
INCREASING REACTIVITY
2
3
Period
number
4
5
6
7
Last pattern
S Last pattern.....the vertical columns
S Called families
S There are 4 of them
1st family
Li
Na
K
Rb
Cs
Fr
Group 1: The Alkali Metals
Location: far left column, group 1
Appearance: shiny, silvery, soft metals
Products: forms water soluble compounds
Reactivity: highly reactive with oxygen and
water
Reactivity Trend: Reactivity increases going
down the group
Ion Charge: 1+
2nd family
Be
Mg
Ca
Group 2:The Alkaline Earth
Metals
Location: second column over from left,
group 2
Appearance: shiny, silvery metals
Sr
Products: forms water insoluble compounds
Ba
Reactivity: less reactive than group 1, will
burn in air if heated
Ra
Ion Charge: 2+
3rd family
F
Cl
Group 17: Halogens
Location: second column from right,
group 17
Appearance: F and Cl are gases, Br is a
liquid, I is a solid
Br
I
At
Reactivity: highly reactive, react
readily with alkali metals
Reactivity Trend: decreases in
reactivity going down group
Ion Charge: 1-
4th family
He
Ne
Ar
Kr
Xe
Rn
Group 18: Noble Gases
Location: Far right column, group 18
Appearance: colourless, odorless gases
Reactivity: most stable and unreactive
elements in the periodic table
Products: Do not form compounds easily
(full outer shell of electrons)
Atom Charge: 0
2.3 The Periodic Table
and Atomic Theory
S
Calculating protons, neutrons
and electrons…a review.
Atomic Number
The number of protons
(same as the number of
electrons in a neutral
atom)
Ion charge
The electric charge of
an atom when it gains
or loses electrons
Average Atomic Mass
The average of the masses of the isotopes
atoms in an element
Add to your notes:
S Atomic number = number of protons (ALWAYS!!!!!!!!)
S Where is “all” the mass contains within an atom?
S What two subatomic particles exists there?
S Therefore,
Atomic mass = number of protons + number of
neutrons
ISOTOPE:
each of two or more forms of the SAME element that
contain equal numbers of protons but DIFFERENT
numbers of NEUTRONS
Remember the Bohr Model?
S The Bohr model of the atom states that:
1. Electrons surround the nucleus
2. Electrons can have only certain energies
energies
energies.
Bohr Model
S In the Bohr model electrons are restricted to “shells”.
Each shell can hold a limited number of electrons.
28
32
18
18
8
Bohr Model
S In a Bohr model of an atom, the electron shells are filled
from the nucleus out with electrons
S One shell is completely filled before any electrons are
placed in the next shell.
What is a Bohr diagram?
•A Bohr diagram is a model of the atom that shows the arrangement of
electrons in each shell, (energy level), surrounding the nucleus
•There is a maximum of two electrons in the first shell, eight electrons in
the second shell, and eight electrons in the third shell.
•Electrons in the outermost shell are called valence electrons.
Steps for drawing Bohr
Diagrams
1. Determine the number of protons,
neutrons and electrons.
2. Draw a nucleus, write the number
of protons and neutrons inside of
it.
3. Fill each energy level with
electrons until you have no
electrons left!
1st
2nd
3rd
4th
Electron shells!
Let’s do these ones together…
Write the answers in your NoBo
He
Li
C
Cl
Patterns in the Periodic Table
1. Which elements have outer shells that are full of electrons? Where are
they located on the periodic table?
2. Which elements have only 1 electron in their outer shell? Where are
they located on the periodic table?
3. What do you notice about the number of valence electrons (electrons in
the outermost shell) for elements belonging to the same family (vertical
column)?
4. Is there a link between the group number (ie. 1 - 18) and the number
of valence electrons an atom has? How are they related?
5. What do you notice about the location of valence electrons for elements
belonging to the same period (horizontal row)?
6. Is there a link between the period number and the number of shells an
atom has? How are they related?
Patterns in the Periodic Table
1. Which elements have outer shells that are full of electrons? Where are
they located on the periodic table?
The Noble Gases have outer shells that are full of electrons, and are
located in group 18.
Patterns in the Periodic Table
2. Which elements have only 1 electron in their outer shell? Where are
they located on the periodic table?
The Alkali Metals have only 1 electron in their outer shell, and are located
in group 1.
Patterns in the Periodic Table
3. What do you notice about the number of valence electrons (electrons in
the outermost shell) for elements belonging to the same family (vertical
column)?
Most elements in the same family (or group) have the same
number of valence electrons
Patterns in the Periodic Table
4. Is there a link between the group number (ie. 1 - 18) and the number
of valence electrons an atom has? How are they related?
The group number number is indicative of the number of valence electrons a
family will have (for elements 1-20).
Look at the last digit in the group number to tell you the # of valence electrons.
Group number 1 (alkali metals) – all elements in this family have 1 valence
electron.
Group number 14 – only look at last digit – 4 valence electrons.
Group number 18, which has 8 valence electrons
Exception to this rule is Helium- it has a full outer shell, but only 2 electrons.
Patterns in the Periodic Table
5. What do you notice about the location of valence electrons for elements
belonging to the same period (horizontal row)?
Elements in the same period have valence electrons in the same shell.
Patterns in the Periodic Table
6. Is there a link between the period number and the number of shells an
atom has? How are they related?
The period number indicates the number of shells that have electrons
Patterns of Electron
Arrangement in Periods
• The period number equals the number of shells in the atom.
1 shell
2 shells
3 shells
4 shells
Patterns of Electron Arrangement in Groups
Except for the transition elements (Groups 3–12), the last digit of the group
number equals the number of electrons in the valence shell.
Examples:
Group 1 = 1 valence electron
Group 13 = 3 valence electrons
Group 14 = 4 valence electrons
Group 15 = 5 valence electrons
Group 16 = 6 valence electrons
Group 17 = 7 valence electrons
By losing or gaining electrons, atoms can have the same number of valence
electrons as the nearest noble gas.
• The noble gas elements have full electron shells and are very stable. They
have a stable octet.
What are Ions?
Ion Formation
•Atoms gain and lose electrons to form bonds.
• The atoms become electrically charged particles
called ions.
• Atoms gain and lose electrons in an attempt to have the same number
of valence electrons (electrons farthest from the nucleus) as the
nearest noble gas in the periodic table.
What are Cations ?
Metals lose electrons and become positive
ions (cations).
BOHR
MODEL
Electrically NEUTRAL
Why?
Charges not balanced
= ION
What are Anions ?
– NON-Metals GAIN electrons
– and become negative ions (anions).
Electrically NEUTRAL
Why?
Charges not balanced
= ION
More Practice
S Checking Concepts (text), p 71
S #5, 8, & 13-16
Homework Check
S Homework: p 71 #5, 8, 13 -16
S 5. (a) Lose
(b) Positive
S 8. The valence shell is the outermost occupied
shell in an atom, while a valence electron is
anelectron that occupies this shell.
S 13. a) Ne – 10p electron arrangement = 2e- 8eb) S – 16 p, e- arrangement = 2e-, 8e-, 6ec) K – 19 p, e- arrangement = 2e-, 8e-, 8e-, 1ed) Be – 4 p, e- arrangement = 2e-, 2e14. a) Neon (Ne)
b) Nitrogen (N)
c) Magnesium (Mg)
S 15. (a) Ar 18p 2, 8, 8
(b) P 15p → → → 2, 8, 5
P3– 15p → → → 2, 8, 8
(c) S 16p → → →
2, 8, 6
S2– 16p → → → 2, 8, 8
(d) Cl 17p → → → →2, 8, 7
Cl– 17p → → → 2, 8, 8
(e) K 19p → → →
2, 8, 8, 1
K+ 19p → → → 2, 8, 8
(f) Ca 20p → → → 2, 8, 8, 2
Ca2+ 20p → → → 2, 8, 8
S 16. The arrangements of the electrons in all ions
in question 15 are identical (2, 8, 8) – all full valence
shells
p. 72 chapter review
Checking Concepts
1. An element is a pure substance made of only
one kind of atom. Specifically, all the atoms of
the element have the same number of protons.
6. Shiny, silver coloured, malleable, ductile, conduct
electricity, conduct heat
7. (a) Carbon, other metals
(b) Steel
10. Atomic mass measures the mass of an atom of
the element.
11. Number of protons = atomic number
12. A chemical family is a group of elements that
have similar chemical and physical properties.
They occur in columns of the periodic table.
13. Alkali metals, alkaline earth metals, halogens,
noble gases
14. Less reactive
15. They are unreactive.
16. A Bohr model represents the arrangement of
electrons in an atom.
17. (a) The valence shell is the outermost occupied electron
shell in an atom.
(b) A valence electron is an electron that occupies
the valence shell.
18. (a) 1
(b) 3
(c) 6
(d) 8
19. (a) Noble gases
(b) Their filled valence shells make the atoms of the
noble gases unreactive.
20. Chemistry is the study of matter and its
changes.
21. Atomic numbers increase from left to right and from
top to bottom through the periodic table.
22. (a) 51
(b) 33
(c) 13
(d) 34
23. Hydrogen (1.0 amu) ; Oxygen (16.0 amu); Nitrogen (14.0 amu);
Rhenium (186.2 amu)
(a) Rhenium
(b) Hydrogen
24. (a) Germanium, neodymium(d) Nickel, germanium
(b) Neptunium
(e) Nickel
(c) Germanium
25. (a) Americium
(b) Iron, ruthenium
(c) Uranium
26. H has the same number of valence electrons as
Li, Na, and K.
27. Be 4p 2, 2
Mg 12p 2, 8, 2
Ca 20p 2, 8, 8, 2
28. (a) Aluminum
(c) Fluorine
(b) Silicon
(d) Neon