Editing Chemical formula (section)

=== Ions in condensed formulae ===
For [[ion]]s, the charge on a particular atom may be denoted with a right-hand superscript. For example, {{chem2|Na+}}, or {{chem2|Cu(2+)}}. The total charge on a charged molecule or a [[polyatomic ion]] may also be shown in this way, such as for [[hydronium]], {{chem2|H3O+}}, or [[sulfate]], {{chem2|SO4(2-)}}. Here + and − are used in place of +1 and −1, respectively.

For more complex ions, brackets [ ] are often used to enclose the ionic formula, as in {{chem2|[B12H12](2-)}}, which is found in compounds such as [[caesium dodecaborate]], {{chem2|Cs2[B12H12]}}. Parentheses ( ) can be nested inside brackets to indicate a repeating unit, as in [[Hexamminecobalt(III) chloride]], {{chem2|[Co(NH3)6](3+)Cl3-}}. Here, {{chem2|(NH3)6}} indicates that the ion contains six [[Metal ammine complex|ammine group]]s ({{chem2|NH3}}) bonded to [[cobalt]], and [ ] encloses the entire formula of the ion with charge +3. {{Elucidate|date=November 2012}}

This is strictly optional; a chemical formula is valid with or without ionization information, and Hexamminecobalt(III) chloride may be written as {{chem2|[Co(NH3)6](3+)Cl3-}} or {{chem2|[Co(NH3)6]Cl3}}. Brackets, like parentheses, behave in chemistry as they do in mathematics, grouping terms together{{snd}}they are not specifically employed only for ionization states. In the latter case here, the parentheses indicate 6 groups all of the same shape, bonded to another group of size 1 (the cobalt atom), and then the entire bundle, as a group, is bonded to 3 chlorine atoms. In the former case, it is clearer that the bond connecting the chlorines is [[ionic bonding|ionic]], rather than [[covalent bond|covalent]].