Question

The melting points for the second series transition elements increase from 1526˚C for yttrium to 2623˚C for molybdenum and then decrease again to 321˚C for cadmium. Account for this trend in terms of band theory.

Answer 1

The melting points of the second series of transition elements are electrons are entering to the type of orbital.

Step-by-step explanation:

Transition elements have "d" band that can overlap with the "s' band to give a composite band. The composite band have six molecular orbitals per metal atom.

Half of the molecular orbitals are the anti bonding.So, maximum bonding occurs when the molecular orbitals contains six electrons i.e. the metal has six valence electrons per each metal atom.

When the maximum bonding occurs then it shows maximum melting point.

So, molybdenum shows melting point at
`2623^(o)C` and after that the electrons goes into the antibonding and reaches minimum for cadmium when the anti boning orbital is completely filled. So, the melting point of the cadmium is tex]321^{o}C[/tex].