2. Bohr Model
Bohr diagrams show how many electrons appear in each electron shell around an atom
The first electron shell holds electrons
The second electron shell holds electrons (Stable Octet)
The third electron shell holds electrons
The fourth electron shell holds electrons
Example Beryllium
4 protons, 5 neutrons 4 electrons 4p 5n

3. BOHR MODELS
Noble gases are very unreactive (stable) because the outer shell is full of electron
Outer shell electrons are called valence electrons
Other atoms gain or lose electrons in order to achieve the stability of noble gases.
Gaining or losing electrons makes atoms into ions

4. Ion Formation RECAP Metals tend to lose electrons and written:
Na+1, Be2+
Positive ions are called CATIONS
Non-Metals tend to gain electrons
O2-, F1-
Negative ions are called ANIONS

5. Draw the Bohr Nitrogen Ion3- 7p
7 n
Nitrogen atom has atomic number of 7 and atomic mass of 14
- 7 protons, 7 neutrons, and 7 electrons
Nitrogen ion has 3- ion charge
gains 3 electrons
So Nitrogen Ion has 7 protons, 7 neutrons, and 10 electrons

6. Draw the Bohr Beryllium Ion2+ 4p 5n
Beryllium atom has atomic number 4 and atomic mass of 9
- 4 protons, 5 neutrons, and 4 electrons
Beryllium ion has 2+ ion charge
loses 2 electrons
So Beryllium Ion has 4 protons, 5 neutrons, and 2 electrons