\({\%~of~an~element} = \frac{mass~of~an~element~in~the~compound}{relative~formula~mass~M_r} \times 100\) There are six atoms of hydrogen in the compound, so the mass ...

The formula of an ionic compound can be deduced from the formulae of its ions. Remember that for the metal elements in groups 1, 2, and 3 the charge on the ion can be deduced by how many outer shell ...