Can dative bond be formed between 2 similar atoms. For example if one oxygen has completed octet by covalent bond with other atom then can this oxygen form dative bond with another oxygen

An oxygen atom can form bonds with other two oxygen atoms to form a compound.

This triatomic oxygen molecule i.e. O₃ is known as ozone.

 

Preparation of ozone:

Ozone is generally prepared when silent electric discharge is passed through the pure, cold and dry dioxygen in special apparatus called ozoniser.
During this reaction, only 10% O₂ is converted to O₃ and product is called ozonised oxygen.

Formation of ozone is endothermic process hence it is necessary to use silent electric discharge.

Structure of ozone:

In ozone, the central oxygen atom is sp² hybridised containing a lone pair of electrons. Hence, ozone has an angular structure with bond angle 117⁰.
It is actually a resonance hybrid.
Because of resonance, both oxygen-oxygen bonds have partial double bond character.