One interesting question that propped up in my mind when I was studying Chemistry was the reason why we exchange valencies (and remove the negative/positive symbols) when we are asked to write the formula of a radical or compound. The book told me that the numbers in the final compound (eg. 2 in CaCl2 or Calcium Chloride) stand for the number of atoms of that element. So, CaCl2 has 1 atom of Ca and 2 atoms of Cl. What has the number of atoms in the compound got to do with the valency of the other element? Well, if you are a chemistry student (in middle school) that has a simple answer. Valency is defined as the number of electrons that can be donated or accepted by an atom to attain the stable electronic configuration of the nearest noble gas. In other words, valency is the number of electrons that an element is willing to take or has the space to take. When you have a valency of 1, and the other atom in the compound, needs 2 electrons, how do you gi...