Periodic Table
Each element is represented by a symbol
- One capital letter – N nitrogen, O oxygen
- One capital letter and one lower case - Na sodium, Ca calcium
Chemical Symbols
-
Short hand way of writing elements and compounds.
Usually it is either the first letter only (capital) or the first (capital) and the
lowercase second letter of the name.
Eg. Calcium – Ca
Hydrogen – H
Some have elements have different symbols because the Latin/Greek
name is used. Eg. Sodium – natrium – Na
Potassium- kalium – K
Iron – ferrum – Fe
Copper – cuprus – Cu
The Periodic Table
Horizontal Rows → called periods. Listed in order of atomic number.
The number of the period is how many energy levels is in each element of that
period.
Example. Hydrogen from period 1 has 1 energy level.
Lithium has 2 energy levels and is in period 2.
Vertical Columns → called groups (1a to 8a) or Families. There are specific
names given to some families based on similar reactions that elements in that
family has.
Group Ia / Alkali Metals - Li,Na,K,Rb,Cs,Fr - this family is very reactive
- Hydrogen is not a metal but is placed over by this family because it
undergoes similar reactions to the elements in this group.
Group IIa / Alkaline Earth Metals – Be,Mg,Ca,Sr,Ba,Ra reactive but not as much
as the alkali metals
Group VIIa / Halogens – F,Cl,Br,I,At
The Diatomic Elements do not want to exist as one atom in nature. F2, Cl2, Br2,
I2, At2, O2 , H2 , N2 , and special cases such as S8 and P4.
Group VIIIa - Noble Gases all elements in this group are gases at room
temperature. They are very unreactive because they have a full outer most
energy level.
The B groups in the periodic table is the Transitional Metals.
There is an imaginary staircase that cuts between boron and aluminum. To the
right of the staircase is the nonmetals and to the left is the metals in the periodic
table.
Metals
three quarters of the
table.
Left side
-shiny
- bendable (malleable)
- good conductors








metalloids
Include
Boron
Silicon
Germanium
Arsenic
Antimony
Tellurium
Polonium
- Neither true metals or
nonmetals
- contain properties of both
Nonmetals
One quarter of the
table. Right side
- dull
- unbendable (brittle)
- not good
conductors
An atom has a neutral or no overall charge. This means that the positive
charges must equal the negative charges, so
The number of protons = The number of electrons
And the number of protons = The atomic number in the periodic table
Atomic number is that number that increases in order as you go across the
horizontal rows. H – 1, He-2, Li –3etc…
Eg. Carbon has atomic number of 6 in the periodic table. This means that there
are 6 protons and 6 electrons in an atom of carbon.
30 Zn 
30p+
and
30e-
Tell the number of protons and electrons in
16S , 35Br, 12Mg, 18Ar, 2He
Atomic Mass
The mass of an atom mostly comes from the nucleus since electrons are so tiny
(2000 times lighter than protons). This means
The # of protons + The # of neutrons = Atomic Mass
Therefore if you know the atomic mass you can calculate the number of
neutrons.
Chlorine
Therefore
-
atomic number = 17
Atomic mass = 35.45
# protons = 17
# electrons = 17
# neutrons = atomic mass - # protons
=
35.45 - 17
=
18.45
The number of protons is equal to the atomic number (number increasing
by one) in the periodic table
The atomic mass may be written superscripted before the symbol
Eg. 18 O form the periodic table you find the atomic number to be 8.
So # protons = 8, # electrons = 8 and # neutrons = 18 – 8 = 10
197
# protons =
# electrons =
# neutrons =
201
# protons =
# electrons =
# neutrons =
Au
Hg
26.98
Al
# protons =
# electrons =
# neutrons =
Express the number of neutrons as a whole number. If decimal places are given
then round them to the nearest whole number.
Complete the following table.
Atom
Mass #
Atomic
(Atomic
number
mass)
14
C
6
16
O
# protons
#
electrons
# neutrons
212
13
4
Po
C
He
12
C
Bohr Rutherford Diagrams / Energy Level Diagrams for Atoms
According to the Bohr Model of the atom electrons may be found at specific
energy levels or distances from the nucleus of an atom. The energy levels
closest to the nucleus contain electrons with little energy while those in the
outer most energy levels have much more energy. Each level contains a
maximum number of electrons:
Levels
Max. # electrons
1 (closest to
2
the nucleus)
2
8
3
8
4
18
The electrons in the outermost levels (furthest from the nucleus) are called
valence electrons.
It is these electrons that will be involved in bonding (how atoms join to form
compounds).
The number of valence electrons = Group Number of the periodic table
Electron Energy Level diagrams may be drawn using the following steps.
1. Draw circle containing the # p ( indicating nucleus ) place the number of
neutrons in here also
2. Write the symbol & particle type below
3. Above the circle write # e- for each energy level
- lower levels fill first
- remaining electrons go in the next levels
Zinc
12e
8e
8e
2e
P 30
N
35
Zn
Carbon
4
2
P6
N6
For the first 3 periods (atomic numbers 1-18) Draw Energy Level Diagrams.
See if you can make a connection between the period number and the energy
levels.
A period is the horizontal rows of the periodic table. Period 1 consists of H, He.
Period 2 consists of lithium to neon. Period 3 consists of sodium to argon etc…