Answer :

To determine which element has six valence electrons, you need to look at the periodic table and identify the element in question.

1. Identify the valence electrons:
- Valence electrons are the outermost electrons of an atom and determine its chemical behavior, particularly its ability to bond with other atoms.

2. Examine the options given:
- Carbon (C)
- Oxygen (O)
- Lead (Pb)
- Phosphorus (P)

3. Match with the correct element:
- Carbon (C) has 4 valence electrons.
- Oxygen (O) has 6 valence electrons.
- Lead (Pb) has 4 valence electrons.
- Phosphorus (P) has 5 valence electrons.

Based on this information, the element with six valence electrons is oxygen (O). Hence, the correct answer is:

Oxygen (O).