Transition metals are generally denser than s-block elements due to their smaller atomic radii and greater atomic masses.

Located in the d-block of the periodic table, transition metals exhibit higher density compared to s-block elements primarily because of their atomic structure. The atomic radius of transition metals is notably smaller than that of s-block elements. This reduction in size occurs because the additional electrons in transition metals are added to the inner d-orbitals rather than the outermost shell. As a result, the outermost electrons are located closer to the nucleus and experience a stronger electrostatic attraction, which effectively decreases the atomic radius.

Moreover, transition metals possess higher atomic masses. The atomic mass is the sum of an atom’s protons and neutrons. Transition metals have a greater number of these subatomic particles compared to s-block elements, which leads to an increased atomic mass.

When evaluating density, it is essential to understand that it is defined as mass per unit volume. Given that transition metals have both a higher atomic mass and a smaller atomic radius, they occupy less volume for a greater amount of matter. This combination results in a higher density compared to s-block elements, which tend to have larger atomic radii and lower atomic masses.

Additionally, transition metals exhibit higher packing efficiency due to their close-packed atomic structures. This characteristic allows their atoms to fit closely together, minimizing empty space between them, further contributing to an increased density.

In summary, the greater density of transition metals compared to s-block elements can be attributed to their smaller atomic radii, higher atomic masses, and enhanced packing efficiency. These factors lead to a larger amount of matter being contained within a smaller volume, resulting in a higher density overall.