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The ability/potential of an atom to pull electron density from a bond shared with another atom towards itself is referred to as its electronegativity.

The electronegative atom bears a partial negative charge and the less electronegative one bears a partial positive charge.

A carbon atom bearing a positive charge on itself is termed as carbocation and the one bearing a negative charge is termed as carbanion.

A carbon atom bonded to atoms having electronegativity higher than carbon leads to the generation of a carbocation and the ones bonded to atoms having less electronegativity than carbon result in the formation of a carbanion.

Heterolysis means the breakage of a bond in which one atom acquires both the shared pair of electrons.

The atom attaining excess electrons will bear a negative charge and the other will acquire a positive charge.

a.

Heterolysis of a carbon-oxygen bond

The heterolysis of the carbon-oxygen (C-O) bond in the given compound generates a carbocation as the electrons shared between carbon and oxygen get transferred to the more electronegative oxygen atom.

b.

Heterolysis of carbon-bromine bond

The bromine atom is more electronegative than carbon and hence the electrons are transferred onto the bromine atom.

Thus, the heterolysis of the carbon-bromine bond generates a carbocation.

c.

Heterolysis of carbon-lithium bond

The carbon atom is more electronegative compared to lithium and hence it will pull the electrons towards itself thereby generating a carbanion.