Which of the following compounds is colourless?

The number of unpaired electrons in $Cr^{3+}$ ion is

What is the observed electronic configuration of $Cu$?

$Ti^{2+}$ and $Ni^{2+}$ have .....

Which of the following is not correct about transition metals?

General electronic configuration of outermost and penultimate shell is $(n - 1)s^2 (n - 1)p^6 (n - 1)d^x ns^2$. If $n = 4$ and $x = 5$,then the number of protons in the nucleus will be: