Question

Question #56d50

Answer 1

Are you asking how to determine formal charge on an ion or a molecule? The question has been covered before.

Explanation:

A neutral oxygen atom has 8 protons, 8 fundamental POSITIVE nuclear charges. To balance this charge there must be 8 corresponding NEGATIVE particles, or 8 electrons. When we write our formula of water, `H_2O`, there is NO formal charge. For `H`, `Z=1`; hydrogen has a share in ONE of the 2 electrons conceived to participate in the `O-H` bond.

By this criterion, oxygen gets 2 electrons, and there are 2 oxygen-based lone pairs (`2` `xx` `2` electrons), which are "owned" by oxygen. So oxygen has 6 electrons so far (i.e. valence electrons) + 2 inner core electrons. Thus oxygen is NEUTRAL. You can usually always easily assign the electrostatic charge by these methods, but this is a first year problem not an A level type of question.

Can you tell me the charge distribution in nitrate anion, `NO_3^-`; there are 25 valence electrons to distribute, and BOTH nitrogen and `2` oxygens have formal charges.