Question

can we calculate formal charge of an atom (which is present in a compound)?

Answer 1

HLO MATE HERE IS UR ANS.

Formal charge = [# of valence electrons] – [electrons in lone pairs + 1/2 the number of bonding electrons]

This formula explicitly spells out the relationship between the number of bonding electrons and their relationship to how many are formally “owned” by the atom. However, since the “number of bonding electrons divided by 2” term is also equal to the number of bonds surrounding the atom, here’s the shortcut formula:

Formal Charge = [# of valence electrons on atom] – [non-bonded electrons + number of bonds].

Let’s apply it to some examples. for example BH4 (top left corner).

   The number of valence electrons for boron is 3.

   The number of non-bonded electrons is zero.

   The number of bonds around boron is 4.

So formal charge = 3 – (0 + 4)  = 3 – 4  = –1

The formal charge of B in BH4 is negative 1.

Let’s apply it to :CH3 (one to the right from BH4)

   The number of valence electrons for carbon is 4

   The number of non-bonded electrons is two (it has a lone pair)

   The number of bonds around carbon is 3.

So formal charge = 4 – (2 +3) = 4 – 5  = –1

The formal charge of C in :CH3 is negative 1.

Same formal charge as BH4!

Let’s do one last example. Let’s do CH3+ (with no lone pairs on carbon). It’s the orange one on the bottom row.

   The number of valence electrons for carbon is 4

   The number of non-bonded electrons is zero

   The number of bonds around carbon is 3.

So formal charge = 4 – (0 +3) = 4 – 3 = +1

You can apply this formula to any atom you care to name.

hope this helps uh dear :)

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