Which of the following is responsible for Metal excess deficiency defect?

Both option 1 and 2 are correct

Non stoichiometric defects: In this type of point defect, ratio of number of cations and anions is not maintained as shown by chemical formula.

There are two types of Non stoichiometric defects

(i) Metal excess: It is created by anion vacancy or extra cation in the interstitial site.

(ii) Metal deficiency: It is created by vacant sites in place of cations or extra anion in vacant site.