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.

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

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 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].

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the answer is:

the farther away a galaxy is from us, the faster it is moving away from us.

definition

                    entropy is a measure of the randomness or the extent of disorder of a chemical process.

                      enthalpy is a measure of the heat change of a reaction occurring at a constant pressure.

measurement units:

                        entropy is measured in joule per kelvin (jk⁻¹)   whereas enthalpy is measured in joule per mole (jmol⁻¹)

requirements:

                            entropy has no requirements or limits, and its change is measured by the division between the heat change of the chemical process and the temperature.

                              in contrast, enthalpy can only be related to the heat change of the reaction under standard conditions.