Which element has the greatest number of valence electrons?

O A. Phosphorus (P)

OB. Oxygen (0)

O

C. Sodium (Na)

O

D. Magnesium (Mg)

Answer: Option B) oxygen (O)

Explanation:

The number of valence electrons in an element refers to the number of electrons in its outermost shell.

Hence, for each of the given elements, they are as follows:

- Phosphorus (P) has an atomic number of 15, with an electronic configuration of 1s2, 2s2 2p6, 3s2 3p3. Hence, it has 5 valence electrons.

- Oxygen (0) has an atomic number of 8, with an electronic configuration of 1s2, 2s2 2p6. Hence, it has 6 valence electrons.

- Sodium (Na), has an atomic number of 11, with an electronic configuration of 1s2, 2s2 2p6, 3s1. Hence, it has 1 valence electron.

- Magnesium (Mg) has an atomic number of 12, with an electronic configuration of 1s2, 2s2 2p6, 3s2. Hence, it has 2 valence electrons.

Thus, oxygen with 6 outermost electrons has the greatest number of valence electrons among the given elements.