Consider the hypothetical molecule abcd. four structures can be drawn for this molecule with the following formal charges.
structure one: a and b have formal charges of +1, whereas c and d have formal charges of -1.
structure two: a and b have formal charges of +2, whereas c and d have formal charges of -2.
structure three: all four atoms have formal charges of zero.
structure four: a and b each have a formal charge of 0, whereas c and d have formal charges of +1 and -1, respectively.
which is the best lewis structure for molecule abcd?

The correct option from the given formula ABCD is the first option out of the four given choices.

Explanation:

The valence electrons are responsible for the formation of a compound lack of electrons in the valence shell of one element and presence of electron in other which both can share.

Now the first option use that the lack of electron in first element is 100 has a positive charge while the other one has one negative charge but share the  electron making both the elements stable in form of a new compound.

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