A way of representing an atoms using its elemental abbr. and dots arranged around it representing valence electrons.
Working out the formula of an ionic compound using Lewis symbols
- represent the cation by removing all the dots from the symbol for the metal atom.
- represent the anion by transferring those dots to the symbol for the nonmetal atom to complete its valence shell.
- (the amounts of atoms of each kind may need to be adjusted for all the dots to be accomodated for.)
- write the charge of each ion as a superscript in the normal way
Note that salts do not form distinct molecules; expressions such as NaCl are merely empirical formulas. Rather, crystal structures involving many atoms are formed, with no distinct molecular units within.
Formulas of compounds consisting of the monoatomic ions of main-group elements can be predicted by assuming that cations have lost all their valence electrons and anions have gained electrons in their valence shells until each ion has an octet of electrons, or a duplet in the case of H, Li, and Be.