Bohr Models

1
Bohr Models
2
Periods

• Tells the number of electrons and their
  arrangement in the orbitals.
• We will make models of these later.

3

• Horizontal rows are called periods
• There are 7 periods

4
Groups

• Elements in same group have the same number of
  valence electrons.
• Similar properties.

5

• Vertical columns are called groups.
• Elements are placed in columns by similar
  properties.

8A
1A
2A
3A
4A
5A
6A
7A
6
Keeping Track of Electrons

• The electrons responsible for the chemical
  properties of atoms are those in the outer energy
  level.
• Called valence electrons
• Core electrons -those in the energy levels below.

Bohn Model
Modern Model
Valence Electrons
Core Electrons
Nucleus
7
Keeping Track of Electrons

• Atoms in the same column have the same outer
  electron configuration.
• Have the same valence electrons.
• Easily found by counting over to their column in
  the periodic table, skipping the transition
  metals.
• The first energy level can hold 2 electrons on
  the outside, the rest can hold 8

8
Valence Electrons of Representative Elements
1
8
2
3
5
6
7
4
9
The Octet Rule Atoms will gain or loose
electrons (whichever is easier) to form a stable
valence shell with 2 or 8 electrons.
1
8
2
3
5
6
7
4
10
Group 1A looses 1 electron for a 1 Charge.
1
2
3
-3
-2
-1
If you loose a negative part, you become positive.
11
Group 2A looses 2 electrons for a 2 Charge.
1
If you loose two negative parts, you become twice
positive.
2
3
-3
-2
-1
12
Group 3A looses 3 electrons for a 3 Charge.
1
If you loose three negative parts, you become
thrice positive.
2
3
-3
-2
-1
13
Group 4A is unique we if often shares electrons
so he will not assign a charge just yet.
1
2
3
-3
-2
-1
14
Group 5A gains 3 electrons for a -3 Charge.
1
If you gain three negative parts, you become
thrice negative.
2
3
-3
-2
-1
15
Group 6A gains 2 electrons for a -2 Charge.
1
If you gain two negative parts, you become thrice
negative.
2
3
-3
-2
-1
16
Group 7A gains 1 electrons for a -1 Charge.
1
If you loose one negative parts, you become once
negative.
2
3
-3
-2
-1
17
Group 8A, the Noble gases will not gain or loose
electrons
1
Since it will not loose or gain, it will never
have a charge!
2
3
-3
-2
-1