Why Tc and Mn have anomalous melting point as compared to tungsten though all have five electrons in d-subshell?

Answer 1

Mn and Tc are both d level elements. That is to say, they are among the elements whose d shells are being filled with electrons. Period 3 is the start of the d shell elements and at period 12, the final d level electron is added. As electrons start to fill the d shell the inter-atomic binding energy builds raising the melting points. That is to say, the attraction between atoms increases, so the atoms are more and more likely to stay close together and organized (a solid). However, with the addition of the 5th d shell electron, the binding energy drops dramatically and the melting point corresponding drops. Both Mn and Tc exhibit this phenomenon. Re (element 75 and a period 7 metal also) does not demonstrate this relative melting point drop due to the much greater radi of the atoms of group 6 and higher.