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:

Step1: Analyze the valence electrons

Elements in the same group have the same number of valence electrons and similar chemical properties. Chlorine (Cl) is in Group 17. Bromine (Br) is also in Group 17, so it has the same number of valence electrons as Cl.

Step2: Analyze other options

• Potassium (K) is in Group 1 (different from Cl's group).
• Magnesium (Mg) is in Group 2 (different from Cl's group).
• Argon (Ar) is a noble gas (Group 18, chemically inert, different behavior from Cl).

Answer:

D. Br, because it has the same number of valence electrons as Cl.