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Why in any transition series, melting points first increase and then decrease and also they sow a dip in the middle ?

Answer» Melting points first increase because the number of unpaired electrons increasesand hence strength of metallic bondincreases. After reaching themaximum, the melting points decrease the pairing of electrons starts in the d-subshell and number of unpaired electrons decreases and so the strength of metallic bond decreases. Thedip in teh middle is due to exactly half-filled configuration of d-subshell which has higher stability . Hence, electrons are held tightly by the nucleus. As a result , metallic bond is weaker.


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