Problem

The correct statement is/are : a. Zirconium (Zr) and hafnium (Hf) have almost same size b. Correct order of ionisation energy of coinage metals is :

\text{Cu} > \text{Ag} < \text{Au}

c. Carbon atom in

\text{CCl}_4

is more electronegative than carbon atom in

\text{CF}_4

\text{Pb}^{2+}

is more stable than

\text{Pb}^{4+}