Question

if na reacts with chlorine to form nacl, which of the following elements reacts with na to form an ionic compound in a one - to - one ratio, and why?
a k, because it is in the same group as na.
b mg, because its mass is similar to that of na.
c ar, because its mass is similar to that of cl.
d br, because it has the same number of valence electrons as cl.

Explanation:

Elements in the same group of the periodic table have similar chemical properties. Sodium (Na) is in Group 1 (alkali metals). Potassium (K) is also in Group 1. When Na reacts with Cl to form NaCl (1:1 ratio), K, being in the same group as Na, will react with Cl in a 1:1 ratio to form KCl. Magnesium (Mg) is in Group 2 (alkaline - earth metals) and will form compounds like MgCl₂ (1:2 ratio). Argon (Ar) is a noble gas (Group 18) and is inert. Bromine (Br) is in Group 17 (halogens) and reacts with metals, but its reaction ratio with Group 1 metals is 1:1 (similar to Cl), but the question is about which element reacts with Na (as a metal) to form an ionic compound in 1:1. However, the key is the group similarity for the metal part. Since the question is about the metal (to form 1:1 ionic compound with Cl, similar to Na - Cl), and K is in the same group as Na.

Answer:

A. K, because it is in the same group as Na.