The periodic table organizes elements according to INCREASING A)
atomic mass.
B)
energy level
C)
atomic number
D)
valence number

C)

atomic number

Explanation:

C)

atomic number is also the number of protons an atom has and this number will never change unlike number of neutrons or 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

the answer your looking for is c).