text: why the transition metals have high melting point, have high density, and forming coloured? why they're called as a collection of metal? transition metals have high melting points because they are metals! all metals have high melting points! but some transition metals have exceptionally high melting points like vanadium and nickiel because they form a partially half filled 3-d subshell (for vanadium) and a fully filled 3-d orbital (for nickiel), which adds to an extra stability to the element. hence, it is more difficult to remove the electron and thus result in the high melting point.    since transition metals are all in the 4th period, its ar would be large too. since ar is large, naturally density would be high.   because mass=no. of molecules x ar   and density is defined as mass / volume.    the specialty of transition mentals is that the energy levels of the orbitals are close enough to overlap each other. when electrons of a transition metal gains energy and is excited, it is promoted to the 4s orbital.    however, it is unstable at that level and soon drops back to the 3d-orbital. in order to return to the 3d-orbital, it must remove some of its energy, and the energy is light. that is why there are different colours in transition metals. because it only releases a specific amount of energy, which relects different colours of light. this process is also known as d-d transition.