Find the number of valence electrons in the Lewis structures of the chlorate ion, ClO₃⁻, the…

Lewis structure: count the valence electrons, adding one per negative charge and taking one per positive charge. Join the outer atoms to the central atom and complete their octets. Put the rest on the centre, and make multiple bonds if the centre is short. Formal charge: $\text{FC} = V - L - \tfrac{1}{2}B$. Exceptions to the octet rule: incomplete octet, odd electrons, expanded octet.