Which element has the same number of valence electrons as calcium?

sulfur
potassium
neon
barium

Barium has the same number of valence electrons as calcium

Explanation:

Valence electrons is the number of electrons of an atom on the outer shell.

Those valence electrons can participate in the formation of a chemical bond (if the outer shell is not closed); in a single covalent bond, both atoms in the bond contribute one valence electron in order to form a shared pair.

Calcium is an atom, part of group 2, called the alkaline earth metals. The alkaline earth metals have 2 valence electrons.

Sulfur is part of a group 16, called the chalcogens or oxygen family. Those atoms have 6 valence electrons. They can form a bound with atoms of group 2 such as calcium, but do not have the same number of valence electrons.

Potassium is part of group 1, called the alkali metals or lithium family. Those atoms have 1 valence electrons. That means  Potassium do not have the same number of valence electrons like calcium.

Neon is part of group 18, the noble gasses. Those are stable atoms, which means they have 8 valence electrons. They do not have the same number of valence electrons like Calcium.

Barium an atom, part of group 2, called the alkaline earth metals. The alkaline earth metals have 2 valence electrons. Calcium is also part of this group.

This means barium has the same number of valence electrons as Calcium.