1. Bohr Model Diagrams of atoms
Part 3 of Atomic Structure
Bromine atom…needs one electron to have an octet in outer shell
Krypton atom…very stable and nonreactive because it has a full octet

2. Special Family Names on the Periodic Table
Alkali Metals = hot orange Semimetals/Metalloids = pink
Alkaline Earth Metals = Faded Blue Halogens = Yellow
Transition Metals = Indigo Noble Gases = Pumpkin Orange
Other Metals = Baby Blue Other Nonmetals = Green

3. ATOMIC STRUCTURE
Electrons are arranged in Energy Levels or Shells around the nucleus of an atom.
first shell a maximum of 2 electrons
second shell a maximum of 8 electrons
third shell a maximum of 8 electrons 3

4. Electrons in larger shells have higher energy levels
1st shell (corresponds to period 1 on periodic table): lowest energy level
2nd shell (period 2)
3rd shell (period 3) ….
7th shell (period 7): highest energy level

5. Drawing Bohr Model Diagrams
You must know the # of protons, neutrons, and electrons
Draw protons (p+), (n0) in circle (i.e. “nucleus”)
Draw the number of energy levels or shells needed (the same as the period it is found in)
Draw dots for electrons into the shells (order of filling is 2,8,8,2 for the first 20 elements He Li
3 p+
4 n0
2e– 1e–
Li shorthand
3 p+
4 n0
2 p+
2 n0
Draw Be, B, Al and shorthand diagrams for O, Na

6. Be B Al O Na 8 p+ 11 p+ 8 n° 12 n° 4 p+ 5 n° 5 p+ 6 n° 13 p+ 14 n°
2e– 8e– 1e– Na
8 p+
8 n°
2e– 6e– O

7. 1. Bohr Models: nucleus and concentric rings
ATOMIC STRUCTURE
There are at least two ways to represent the electron arrangement of an element or compound;
1. Bohr Models: nucleus and concentric rings
2. Electron Configuration: summary of # of electrons in each shell like 2,8,8, 1 for potassium (K) 7

8. ELECTRONIC CONFIGURATION
Write the electronic configuration for the following elements; 40 23 16 Na O Ca a) b) c) 8 11 20
2,8,8,2
2,8,1
2,6 35 28 11 Cl Si B d) e) f) 5 17 14
2,8,7
2,8,4
2,3 8

9. SUMMARY The Atomic Number of an atom = number of
protons in the nucleus.
The Atomic Mass of an atom = number of
Protons + Neutrons in the nucleus.
The number of Protons = Number of Electrons.
Electrons orbit the nucleus in shells.
Each shell can only carry a set number of electrons. 9