Instead of accepting the atomic mass of indium implied by the data in Exercise 51, Mendeleev proposed that the formula of indium oxide is In₂O₃. Show that this assumption places indium in the proper group of Mendeleev’s periodic table on page 378.

Exercise 51

In Mendeleev’s time, indium oxide, which is 82.5% In by mass, was thought to be InO. If this were the case, in which group of Mendeleev’s table should indium be placed?