Which element is most likely to form a cation?

sodium, silicon, sulfur, argon

Sodium

Explanation: To answer the question we need to know a few things.

What are cations?

Cations are positively charged ions that are formed when an atom of an element loses an electron (s).

What elements form cations?

Metallic elements form cations since they react by losing electrons thus forming ions with a positive charge. For example, alkali metals such as sodium form cations with a charge of + 1. In this case, sodium will form a cation with a charge of + 1, Na⁺

What are negatively charged ions?

Negatively charged ions are known as anions. They are formed by non-metallic elements such as sulfur, argon, silicon, etc.