Assign a reason for each of the following observation :
(i) The transition metals are hard and have high melting and boiling points
(ii) The ionisation enthalpies (first and second) in the first series of the transition elements are found to vary irregularly

Explanation

(i) Transition metals have high melting and boiling point and are hared to strong metallic bonds between the atoms of these elements .Greater the unpaired electrons stronger the metallic bond
(ii) The irregular trend is due to the fact that removel of e -s alters the relative energy of 4s and 3d there is reorgansiation energy accompanying ionisation .Thuis result in relaease of has low I.E because a loss of one e gives stables configuation .Zn has very high I.E because electronn has to to be removed from 4s stable configuration