https://byjus.com/questions/find-the-mendeleevs-periodic-table-group-number-of-the-following-elements-from-their-hydrides-and-oxides-formula/
https://byjus.com/questions/find-the-mendeleevs-periodic-table-group-number-of-the-following-elements-from-their-hydrides-and-oxides-formula/