Invar,an alloy of $Fe$ and $Ni$,is used in watches and meter scales. Its characteristic property is:

Which of the following is a coloured compound?

Which of the following ions exhibit the same value of spin-only magnetic moment? $(A)$ $Ti^{3+}$, $(B)$ $Cr^{3+}$, $(C)$ $Mn^{2+}$, $(D)$ $Fe^{3+}$, $(E)$ $Sc^{3+}$. Choose the most appropriate answer from the options given below.

The "spin-only" magnetic moment [ in units of Bohr magneton,$(\mu_B)$ ] of $Ni^{2+}$ in aqueous solution would be (At. No. $Ni = 28$).

$Zn$ and $Cd$ metals do not show variable valency because

$d$-block elements form alloys easily because......