SSC MTS EXAM

Detailed explanation-1: -If a compound contains more than one polyatomic ion of the same type, we need to place parentheses around the ion’s formula before using a subscript to indicate how many ions of that type are in the compound.

Detailed explanation-2: -Polyatomic ions in chemical formulas are enclosed in parentheses followed by a subscript if more than one of the same type of polyatomic ion exist. Molecular formulas do not indicate how the atoms are arranged in the molecule. The empirical formula tells the lowest whole-number ratio of elements in a compound.

Detailed explanation-3: -Very often in chemical formulae, we use parentheses to form subgroups of atoms within a molecule. Usually this has some meaning about the structure of the molecule, but don’t worry about that for now. Parentheses are useless in a chemical formula if they don’t have a subscript, so we’ll assume one is always there.