Question

Consider the Lewis structure below. What are the formal charges of each atom?

Answer 1

H = +1 (B)
O = -2 ( D)
C = +2 ( A)
N = -3 (G)

Explanation:

The Hydrogen loses one electron to the Oxygen which has a higher electron negativity
The Hydrogen loses one electron to the Carbon as well which also has a higher electron negativity.

The Oxygen gains one electron from the Hydrogen and one electron from the Carbon both of which have lower electron negativity.

`O = -1 + -1 = -2`

The Carbon gains one electron from the Hydrogen (-1) and loses one electron to the Oxygen ( +1) and loses two electrons to the Nitrogen.

`C = -1 + 1 + 2 = +2`

Nitrogen gains two electrons from the Carbon ( -2) and one electron from the Hydrogen (-1)
`N = -2 + -1 = -3`

The total molecule will have an approximate value of zero so the charges should add up to zero.

`3 xx H = 3 xx +1 = +3` 1 xx O = 1 xx -2 = -2
`1 xx C = 1 xx +2 = +2` 1 xx N = 1 xx -3 = -3

Adding all of these up
`+ 3 + -2 + 2 + -3 = 0`

Answer 2

The formal charge on every atom is zero.

Explanation:

Formal charge is the charge that an atom appears to have when its valence electrons are counted according to certain arbitrary rules:

• Lone pair electrons belong entirely to the atom.
• Half of the shared bonding electrons belong to the atom.

In symbols, you get the formula

`color(blue)(bar(ul(|color(white)(a/a) FC = VE – LP – 1/2BEcolor(white)(a/a)|)))" "`

where

`VE =` the number of valence electrons in an isolated atom
`LP =` the number of lone pair electrons
`BE =` the number of bonding electrons

For `"H", FC = 1- 0 -2/2 = 0`

For `"C", FC = 4 - 0 - 8/2 = 0`

For `"N", CF = 5 - 2 - 6/2 = 0`

For `"O", FC = 6 - 4 - 4/2 = 0`