Which of the following properties is not expected to be shown by copper?

The metal commonly present in brass and german silver is

Which of the following will be a coloured ion?

Which of the following elements form interstitial compounds?

Which pair of ions gives a blue colour in an aqueous state?
$V^{+4}, Ni^{+2}, Ti^{+3}, Co^{+2}, Fe^{+3}, Cu^{+2}$

The spin-only magnetic moment value of the ion among $Ti^{2+}$,$V^{2+}$,$Co^{3+}$,and $Cr^{2+}$ that acts as a strong oxidizing agent in aqueous solution is .......... $BM$ (nearest integer).
(Given atomic numbers: $Ti = 22, V = 23, Cr = 24, Co = 27$)