Lewis Structures

– Hydrogen and the halogens bond once. – The family oxygen is in bonds twice. – The family nitrogen is in bonds three times. The

family carbon is in bonds four times. – Hydrogen will never be in the center– Otherwise, start with the first element in the

formula in the center

• Draw the EDD for each atom in the compound• Add up the number of electrons in the

compound.• Put the first non hydrogen element in the center

and build off of it.• Bond any free electrons together as a bond• Make sure that each element obeys the octet

rule• A resonance structure is a structure that occurs

when it is possible to write two or more electron dot diagrams for the same molecule or ion

Resonance Structures• A resonance structure is a structure that

occurs when it is possible to write two or more electron dot diagrams for the same molecule or ion

Lewis Structures1. First figure out the total number of electrons available for bonding

by writing the electron dot diagram for each element2. Next figure the total number of atoms to get the noble gas

configuration for each atom.3. Subtract the first number from the second to get the total number of

bonding electrons.4. Divide that by 2, that is the number of bonds in the Lewis structure5. When writing the bonds, hydrogen and halogens bond once, oxygen

group bonds twice, nitrogen group 3 times, and carbon group 4.6. To get the number of unbonded electrons, subtract 3 from 17. Pick the central atom, and write it first8. Write in the bonds to give noble gas configuration9. Write in any unshared electron pairs.