If atoms of a halogen nonmetal gain one electron, the atoms then have how many valence electrons?

the dissociation of nickel hydroxide is follows:

the concentration of hydroxide ion is

the equilibrium constant value of nickel hydroxide is = 6.1 * 10^-^1^6 and thus equilibrium equation can be written as:

thus, concentration of ni is 0.23 * 10^-^4 mol /l

50.23 i believe is correct but don't quote me on that.