i. The densities of d-block elements are relatively higher as compared to the s-block elements due to the decrease in the size of the atoms and the consequent increase in the nuclear charge, which results in the compact structure of the elements.
ii. The density of the atoms increases with the decrease in the size of the atom. Therefore the density of the elements increases from left to right across a period.
iii. Transition elements form strong metallic bond in which both (n–1) d and ns electrons take part.
iv. Due to the notable covalent character of the strong metallic bond, considerable amount of energy is required to break the metallic bond in order to melt the metal. Hence, these metals possess high melting and boiling points.
Note: Atomic properties of 3d series: