The calculated magnetic moment of Cu²⁺ ion
is

Electronic configuration of Cu²⁺ is 1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d⁹

The magnetic moment is given by, $\sqrt{n(n+2)}$ where, n= the number of unpaired electrons.

Therefore, the magnetic moment of Cu²⁺ is, n=1,since the number of unpaired electrons in cu²⁺ is 1.

$\sqrt{1(1+2)}$=$\sqrt{3}$=1.73 B.M.

Hence , the correct option (A).