91Ó°ÊÓ

Condensed structures display atoms but few, if any, bonds.

Skeletal structures display bonds but few, if any, atoms.

In all the given questions, carbon is the central atom moving along the parent chain, which is the chain containing the greatest number of carbon atoms in succession.

We know as per rules for Lewis structures:

1. Carboncan form 4 bonds as it has 4 valence electrons.
2. Oxygen has 2 lonepairsand 2 unpaired electrons, and so can form 2 bonds.
3. Hydrogen will form 1 bond as it has 1 valence electron.
4. Nitrogen will form 3 bonds as it has zero formal charge.

According to the octet rule, atoms gain or lose electrons in order to achieve an outer shell electron configuration that is closest to that of a noble gas. The skeletal structures are made keeping this rule in mind.