1. Bohr Models, Valence and the Octet Rule

2. Bohr Models Recall: Atomic number = number of protons;
Mass number = protons + neutrons;
Number of electrons = number of protons (in a neutral atom)
Electrons are in energy shells

3. Bohr Models 1st energy shell can hold a maximum of 2 electrons
2nd energy shell can hold a maximum of 8 electrons
3rd energy shell can hold a maximum of 18 electrons

4. Bohr Models
Draw Bohr models to see the placement of electrons in their energy shells
Example: Carbon C
6 p+
6 n°
2e-
4e-

5. Bohr Models Bohr Models Draw the Bohr model for Sodium (Na) Na 11 p+

6. Valence Electrons
Valence electrons are the electrons that occupy the outermost energy level
Valence electrons are involved in bonding Na
11 p+
12 n°
2e-
8e-
1e-

7. Valence Electrons How many valence electrons does oxygen have? O 8 p+

8. Octet Rule
The most stable electron configuration is one that has a full outer shell
Atoms will combine with each other in order to achieve a full outer shell
Atoms can either lose or gain valence electrons
Noble gases are the only elements that do not need to bond because their outer shells are already full

9. Octet Rule
How many electrons does sodium need to lose in order to have a full outer shell?
Sodium needs to lose this one valence electron to have a full outer shell. Na
11 p+
12 n°
2e-
8e-
1e-

10. Chlorine needs to gain one electron to have a full outer shell.
Octet Rule
How many electrons does chlorine need to gain in order to have a full outer shell?
Chlorine needs to gain one electron to have a full outer shell. Cl
17 p+
18 n°
2e-
8e-
7e-
1e-

11. Octet Rule
If sodium gives its valence electron to chlorine, they both satisfy the octet rule and they become bonded as NaCl. Na
11 p+
12 n° Cl
17 p+
18 n°
2e-
8e-
1e-
7e-
8e-
2e-