Question

Transition metal complexes containing, $C{{N}^{-}}$ ligands are often yellow in colour, whereas those containing ${{H}_{2}}O~$ ligands are often green or blue. This is because $C{{N}^{-}}$ is a strong ligand. Absorption takes place near UV (blue) , so they appear yellow.
If true enter 1, else enter 0.

Answer 1

The colour of the compounds is determined by the d-d transitions in the atoms present in the compounds or the ligands. Variations occur in the transitions and so in the colour of the compounds.

Complete step by step solution:
-The electrons are responsible for the characteristics of the compounds and the molecules as they are loosely held and can be easily removed, gained or shared. They are filled according to different rules like aufbau’s principle, hund’s rule and pauli’s principle.
-There are 4 quantum numbers n, l, m and s. The principal quantum number (n) tells us about the shells of the atom. The azimuthal quantum number (l) tells us about the subshells of the atom. The magnetic quantum number (m) tells us about the orbitals of the atom and the spin quantum number (s) tells us about the orientation of the electrons in the orbital.
-Third quantum number is magnetic quantum number and is denoted by m. It gives us the exact orbitals. Its total value can be given as ${{n}^{2}}$ or as (2l+1) since it lies in the range (-l to +l).
-Transition elements are formed by the d-block elements and they show d-d transitions due to the different unpaired electrons present in the elements. These unpaired electrons show transitions from one energy state to the other leading to the change in the energy difference thereby releasing the energy as well as photons.
-The colour of the compounds formed depend on the energy released during the transitions. The ligands in the question have different energy band gaps. Photons below this energy bandgap will not be absorbed and those above this will get absorbed.
-Transition metal complexes containing, $C{{N}^{-}}$ ligands are often yellow in colour, whereas those containing ${{H}_{2}}O~$ ligands are often green or blue. This is because $C{{N}^{-}}$ is a strong ligand. Absorption takes place near UV (blue) , so they appear yellow.

Therefore the given statement is true and hence 1.

Note: The colour of the compound depends on the d-d transition but only in the complex formation. When we consider the compound in solid state, then the orientation of the compound molecules is different as they are present in the crystal lattice where every atom has a fixed position for itself. So colour formation in such compounds do not need d-d transitions.