Final answer:
The five elements that do not follow the octet rule are Hydrogen, Lithium, Beryllium, Boron, and Phosphorus. They have fewer or more than eight valence electrons and follow the duet rule or incomplete octet rule.
Step-by-step explanation:
The five elements that do not follow the octet rule are:
- Hydrogen
- Lithium
- Beryllium
- Boron
- Phosphorus
These elements do not follow the octet rule because they have fewer or more than eight valence electrons. Hydrogen only needs two valence electrons to have a full outer shell, so it does not need to form any additional bonds. Lithium, beryllium, and boron are exceptions because they can form stable compounds with fewer than eight valence electrons. Phosphorus can form stable compounds with more than eight valence electrons.
The rule that these five elements follow is known as the "duet rule" for hydrogen and the "incomplete octet rule" for lithium, beryllium, boron, and phosphorus.