1. Most plausible! Cyanate NCO- -1 Non-Equivalent Resonance Structures -1-1
NCO-
Non-Equivalent Resonance Structures -1
Most plausible! +1 -2

2. Equivalent Resonance Structures
(The formal charges don’t really change!)

3. Boron trifluoride
BF3
Disobeys the Octet Rule (in a deficient manner)

4. sulfur hexafluoride SF6
Disobeys the Octet Rule (in an excessive manner)

5. The Principle of Electroneutrality:
Formal Charge = Representative - # of lone - 1/2 of the
Group # pair bonding
electrons electrons
The Principle of Electroneutrality:
1. Atoms in molecules (or polyatomic ions) should have formal charges as close to zero as possible
2. A molecule is most stable when any negative formal charges reside on the most electronegative element

6. Important points to consider:
1. Carbon, nitrogen, oxygen and fluorine always obey the octet rule!
2. Boron and beryllium can disobey the octet rule in a deficient manner!
3. Third period elements (or beyond) can disobey the octet rule in an excessive manner if needed.