Amalgam Electrodes

Amalgams are

During electrolysis of aqueoussolution of NaCl in presence of platinum electrodes , hydrogen is evolved at tha cathode , but in presence of mercury as cathoelede , sodium amalgam is produced during electrolysis Why ?

Amalgams are:

During the electrolysis of NaCl , when platinum electrode is taken, H_2 , is liberated at the cathode while-it form sodium amalgam with mercury cathode. This is because

Amalgams are the example of: