Question

How can you name chemical compounds from their formulae in the following cases?

Give examples in support of your answer

If a compound contains only two elements(binary compounds) such that one of them is metal.

Answer 1

Definition of formulae

A chemical formula tells us the number of atoms of each element in a compound. It contains the symbols of the atoms of the elements present in the compound as well as how many there are for each element in the form of subscripts.

Naming chemical compounds

• It is a method of providing information about the chemical proportions of atoms that make a particular chemical compound or molecule by chemical element numbers and symbols.
• An ionic compound that contains only two elements, one present as a cation (i.e metal) and one as an anion, is called a binary ionic compound. One example is ${\text{MgCl}}_2^{}\text{(Magnesium chloride)}$.
• For binary ionic compounds, the subscripts in the empirical formula can also be obtained by cross multiplying charges: use the absolute value of the charge on one ion as the subscript for the other ion.
• When cross multiplying charges, it is sometimes necessary to reduce the subscripts to their simplest ratio to write the empirical formula. Consider, for example, the compound formed by ${\mathrm{Mg}}^{2+}$ and ${\mathrm{O}}^{2-}$. Using the absolute values of the charges on the ions as subscripts give the formula ${\mathrm{Mg}}_2{\mathrm{O}}_2$
• This simplifies its correct empirical formula MgO (Magnesium oxide). The empirical formula has one ${\mathrm{Mg}}^{2+}$ ion and one ${\mathrm{O}}^{2-}$ ion.