Establish the formula for a metal halide dihydrate if it is known that one of its ions has the electronic configuration

Establish the formula for a metal halide dihydrate if it is known that one of its ions has the electronic configuration 1s22s22p63s23p6, and the mass of the metal in it is 3.81 times greater than the mass of water.

Given:
MeHalx * 2H2O
m (Me) / m (H2O) = 3.81

To find:
MeHalx * 2H2O -?

Decision:
1) Let n (MeHalx * 2H2O) = 1 mol;
2) n (Me) = n (MeHalx * 2H2O) = 1 mol;
3) m (Me) = n (Me) * M (Me) = 1 * M (Me) = M (Me);
4) n (H2O) = n (MeHalx * 2H2O) * 2 = 1 * 2 = 2 mol;
5) M (H2O) = Mr (H2O) = Ar (H) * N (H) + Ar (O) * N (O) = 1 * 2 + 16 * 1 = 18 g / mol;
6) m (H2O) = n (H2O) * M (H2O) = 2 * 18 = 36 g;
7) m (Me) / m (H2O) = 3.81
M (Me) / 36 = 3.81;
M (Me) = 137 – Ba;
8) 1s2 2s2 2p6 3s2 3p6 – Cl–;
9) Unknown substance – BaCl2 * 2H2O.

Answer: Unknown substance – BaCl2 * 2H2O.