Valence electrons in the element A are 3 and that in element B are 6. Most probable compound formed from A and B is

Valence electrons in A = 3Valence electrons in B = 6Thus, A is electropositive and B is electronegative, A can lose three electrons and B can gain two electrons to attain stable configuration.Thus, A exists as ,A3+ and B as B2-Thus, compound is A2B3.