Question 6
What is the chemical formula of beryllium chloride?
The right answer is the one marked above.
BeCl2. Beryllium has a valency of 2 and chlorine of 1. Crossing over puts the 2 on the chlorine and the 1 on the beryllium.
Chlorine's valency is given as 7, 1 — here it is acting with a valency of 1, as it does in every chloride. Calcium chloride works the same way: Ca is 2, Cl is 1, giving CaCl2.