If the radius of `Mg^(2+)` ions, `Cs^+` ion, `O^(2-)` ion, `S^(2-)` ion and `Cl^-` ion are 0.65 `A^0`, 1.69 `A^0`, 1.40 `A^0 `, 1.84 `A^0` and 1.81 `A^0` respectively, then calculate the Coordination number of cations in crystal of MgO, MgS and CsCl and Mgs