Unlike s-block metals, have very high melting and boiling points they

Options

A. are more meltallic
B. are more dense
C. utilize (n-1) d as well as ns electrons for boiling
D. have higher ionization enthaplies

Answer

C

Explanation

The high melting and boiling points of d-block elements are attributed to the stronger forces that bind their atoms together. Besides metallic bonding through the use of ns electrons, d-block metals engage themselves in convalent bonding through the use of their (n-1) d electrons. Therefore, the presence of one or more unpaired (n-1) d electrons contributes to higher interatomic force on account of covalent bonding and therefore, to higher melting and boiling points. Thus, with increasing availability of the unparied d electrons, the strength of the interatomic bonding increases, resulting in higher melting points. Consequently, when we move across any series in the d-block, the melting point increases, rises to a maximum value near the middle of each series and then it decreases on account of pairing of (n-1) d electrons. However, Mn and Tc have abnormally low melting points on account of their copmplex crystal structures. Among the d-block metals, the melting points of Zn, Cd and Hg are abnormally low due to non availability of unpaired (n-1) d electrons for covalent bonding.