Which element would you expect to be less metallic?

(a) Sb or As (b) Si or P (c) Be or Na

When we move across a period from left to right then there will occur an increase in electronegativity and also there will occur an increase in non-metallic character of the elements.

As both arsenic (As) and antimony (Sb) are group 15 elements. And, on moving down the group increases metallic character hence, Sb will be more metallic than As. Therefore, As is less metallic in nature than Sb.

Silicon (Si) is a group 14 element and phosphorus (P) is a group 15 element. And, both of them lie in period 3 and since, non-metallic character increases on moving from left to right along a period. Therefore, phosphorus (P) is less metallic than silicon (Si).

Sodium (Na) is a group 1A element (also known as alkali metal) and beryllium (Be) is a group 2A element (also known as alkaline earth metal). Hence, Be is less metallic than Na because on moving from left to right there occurs an increase in non-metallic character.