(a) Following is the alignment of magnetic moments of a substancewhen placed in a magnetic field. Identify the type of magnetismexhibited by the substance.

(b) Analysis shows that nickel oxide has formula Ni_0.98O_1.00. What

fractions of nickel exist as Ni⁺² and Ni⁺³ ions ?

(a) When the magnetic moments are all aligned upwards in the same direction, ferromagnetism is shown.

(b) Given, the formula of nickel oxide is Ni_0.98 O_1.00.

So the ration of atoms of Ni and O are Ni:O = 98:100.

Thus, for 1 atom of oxygen there are0.98 atoms of Ni.

Let us consider the number of atoms of Ni⁺²to be x.

Then number of atoms of Ni³⁺ = (0.98–x). [As total Ni atoms are 0.98]

As always, total charge on cation (Ni²⁺ and Ni³⁺)= Total charge on anion (O^2-)

So,

∴

So, x = 0.94 = No. of Ni²⁺ions.

No. of Ni³⁺ ions = 0.98-x = 0.98-0.94 = 0.04

Thus, fraction of Ni²⁺ existing =

Similarly, fraction of Ni³⁺ existing =