Transition elements melting and boiling points of transition elements

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Melting and boiling points : 

Transition elements , have high melting and boiling point as compared to normal element . The malting and boiling point , however increase and decrease to a maximum value (elements with five unpaired electron) and then falls as the atomic numbers increase in a series . This is due to the strong metallic bond between their atom . As the strength of metallic bond depend upon the number of unpaired electron (or, half field d-orbitals)5, the number of unpaired electron increase upto d configuration (e.g. , Cr in the first series ) and then decrease upto d configuration (e.g., Zn in the first series) and therefore , the melting point and boiling point increase upto Cr and then decrease to Zn , Cd , and Hg, all the d- orbital are completely failed , no electrons are available for co-valent bonding (metal bonding) amongst the atoms of these elements. Thus , these elements have very low melting point and boiling point in their respective transition series.

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