Which of the following is the correct formula for Ca2+ reacting with NO2?? O A. Ca NO2
O B. Ca(NO2)2
O C. Ca (NO)
O D. CaNO2

B. Ca(NO2)2

Explanation:

Ions (charged atoms) combine with one another to form stable ionic compounds. In this case, calicium ion (Ca2+) is said to react with NO2, which has a charge of -1 i.e. +1-1(2) = 1-2 = -1.

This means that calcium has a charge of +2 while nitrite ion has charge of -1, hence, when they combine, they exchange their charges, which become their subscript as follows:

Ca2+ + NO2- → Ca(NO2)2

Ca(NO2)2 is a stable ionic compound called calcium nitrite. Notice that it takes two atoms of NO2- to react with one atom of Ca2+.

the answer is c.the valence of the atoms combine .