Question

If the following ion(s) is/are coloured enter 1, else enter 0.

$C{a}^{2+}$

Answer 1

$C{a}^{2+}$ is white in colour. Its electronic configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^6$ and excited state configuration is $1s^{2}2s^{2}2p^{6}3s^{2}3p^{5}4s^1$.

In order to absorb visible light, an electron would have to move to a higher energy orbital . The difference in energy of the orbitals would have to equal the energy of a visible wavelength photon. For p to s orbital shift, the energy difference is much higher that an electron could move and would correspond to UV light. Therefore, $C{a}^{2+}$ do not exhibit any colour in aqueous solution and is white in solid state.