The mass fraction of oxygen in the higher oxide of an element of group V of the periodic

The mass fraction of oxygen in the higher oxide of an element of group V of the periodic system of D.I.Mendeleev is 16.06%. What element is it?

Given:
E2O5 – higher oxide of a group V element
ω (O in E2O5) = 16.06%

To find:
NS – ?

1) ω (E in E2O5) = 100% – ω (O in E2O5) = 100% – 16.06% = 83.94%;
2) Let Ar (E) = (x);
3) Mr (E2O5) = Ar (E) * N (E) + Ar (O) * N (O) = x * 2 + 16 * 5 = (2x + 80);
4) Ar (E) = (ω (E in E2O5) * Mr (E2O5)) / (N (E in E2O5) * 100%);
x = (83.94% * (2x + 80)) / (2 * 100%)
200x = 167.88x + 6715.2;
32.12x = 6715.2;
x = 209;
5) Ar (E) = x = 209;
6) Unknown element – Bi – bismuth.

Answer: Unknown element – Bi – bismuth.