Why are transition elements hard and do they possess high melting and boiling points?

(N/A) In transition elements,the strength of the metallic bonds depends on the number of unpaired electrons. The greater the number of unpaired electrons in the $(n-1)d$ subshell,the stronger the metallic bonding and the greater the bond strength. This increases the hardness of the metal.
The high melting points of these elements are due to strong metallic bonds between the atoms,which exhibit significant covalent character. Consequently,a large amount of energy is required to break these bonds to melt the metals.
Within a period,the melting points of transition elements generally increase with the number of unpaired electrons in the $(n-1)d$ subshell. For instance,in the first transition series,chromium $(d^5)$ has a high melting point and is a hard metal due to its maximum number of unpaired electrons.
After the middle of the series,the electrons begin to pair up,which results in a decrease in the strength of the metallic bonds. Hence,the melting points start to decrease.
Elements like $Zn$,$Cd$,and $Hg$ are soft and volatile because they have no unpaired electrons in their $(n-1)d$ subshell,leading to weak metallic bonding and low melting points.