Final answer:
Each element has a specific number of valence electrons that determines its chemical bonding behavior. Oxygen has 6, calcium has 2, phosphorus has 5, argon has 8, chlorine has 7, and boron has 3 valence electrons. The octet rule applies to most elements, seeking 8 valence electrons, but there are notable exceptions.
Step-by-step explanation:
Valence electrons play a critical role in chemical bonding and in determining the structure of molecules. An unbonded atom has a certain number of valence electrons which can be determined by its position on the periodic table. Here's the list of the given elements with the correct number of valence electrons:
- Oxygen (O) - 6 valence electrons
- Calcium (Ca) - 2 valence electrons
- Phosphorus (P) - 5 valence electrons
- Argon (Ar) - 8 valence electrons
- Chlorine (Cl) - 7 valence electrons
- Boron (B) - 3 valence electrons
Most elements aim to fulfill the octet rule, which says they are most stable with 8 valence electrons. However, there are exceptions like hydrogen (preferring 2 valence electrons, commonly known as the duet rule), as well as boron and beryllium sometimes having fewer than 8 valence electrons in their compounds. On the other hand, elements from the third period and beyond can have more than 8 valence electrons, as they have access to d or f orbitals.