Plz ans 18 and 19 with explanation

19 ans what

See Priyanshi A₂B₅ means A⁵⁺ and B^2-. So for A we have 5 electrons in the outermost shell for A and in case of B^2- , it falls in the O^2- group. Thus it will have 6 electrons in its outermost shell.

See Priyanshi, if element A has 3 electrons in the outermost shell ,then it will have charge A³⁺,that u too know about it. Now if element B has 6 electrons in the outermost shell , then it will have B^2-, cause removing 2 electrons is easier than removing 6 electrons, you konw that. Thus the element thus formed will be:- A₂B₃. Hope it helps you...^_^