Transition metals have higher melting and boiling points. This is due to strong overlapping between (n-1)d orbitals and formation of covalent bonds by the d electrons. Greater the number of unpaired d electrons , greater the possibility of covalent bond formation, hence the higher m.p. and b.p. Zn, Cd and Hg are notable exceptions because in these elements the (n-1)d orbitals are complete and covalent bond formation in d orbitals is not expected. In a period, they reach a maximum near group VB, and VIB. In moving across a transition series from left to right the number of unpaired d electrons rises to maximum of five in group VI beyond which electrons paring begins. The number of unpaired d electrons in each atom the magnitude of binding forces by forming covalent bonds with unpaired electrons of neighboring atoms.
Posted on: Mon, 16 Sep 2013 12:30:01 +0000
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