Question

the octet rule

• atoms are most stable when they have a full outer shell of valence electrons.
• most atoms will attempt to have a full outer shell of eight valence electrons.
• atoms will gain or lose electrons to fulfill the octet rule.
• atoms seek to gain or lose the fewest electrons possible in becoming stable.

example: draw a lewis dot structure for each element below. indicate whether the
element will gain or lose electrons to have a full outer shell, and identify how many
electrons it will gain or lose.
bromine calcium
lithium oxygen

Explanation:

Bromine

Step1: Determine valence electrons

Bromine (Br) is in group 17. Valence electrons = 7. Lewis dot structure: $\cdot \cdot \cdot \cdot \cdot \cdot \cdot$ (7 dots around Br symbol).

Step2: Analyze electron gain/loss

To reach octet (8 electrons), it needs 1 electron. So, it will gain 1 electron.

Calcium

Step1: Determine valence electrons

Calcium (Ca) is in group 2. Valence electrons = 2. Lewis dot structure: $\cdot \cdot$ (2 dots around Ca symbol).

Step2: Analyze electron gain/loss

To reach octet, losing 2 electrons (easier than gaining 6). So, it will lose 2 electrons.

Lithium

Step1: Determine valence electrons

Lithium (Li) is in group 1. Valence electrons = 1. Lewis dot structure: $\cdot$ (1 dot around Li symbol).

Step2: Analyze electron gain/loss

To reach octet (for Li, a full outer shell can be 2 electrons as it's in period 1, but following octet rule concept here), losing 1 electron (easier than gaining 7). So, it will lose 1 electron.

Oxygen

Step1: Determine valence electrons

Oxygen (O) is in group 16. Valence electrons = 6. Lewis dot structure: $\cdot \cdot \cdot \cdot \cdot \cdot$ (6 dots around O symbol).

Step2: Analyze electron gain/loss

To reach octet, it needs 2 electrons. So, it will gain 2 electrons.

Answer:

• Bromine: Lewis dot structure with 7 dots, gains 1 electron.
• Calcium: Lewis dot structure with 2 dots, loses 2 electrons.
• Lithium: Lewis dot structure with 1 dot, loses 1 electron.
• Oxygen: Lewis dot structure with 6 dots, gains 2 electrons.