Question

When a chemical symbol in a chemical formula has no subscript, what does it mean?

Answer 1

That there is only the one such atom in the formula unit.

Explanation:

So we take a common ionic material such as calcium fluoride, `CaF_2`. In one formula unit there is the one `Ca^(2+)` ion, and `2xxF^-` ions.

In one mole of calcium fluoride, there are one mole of `Ca^(2+)` ions, and two moles of `F^-` ions. How many moles of ions (calcium and fluoride) are in one mole of `CaF_2`?