Which transition metal has the highest density? A) Zn B) Sc C) La D) Os

The correct answer is D) Os (Osmium).

Explanation:
Density is a property that depends on both the atomic mass and the atomic radius of an element. Transition metals, especially those in the middle of the d-block, tend to have high densities because they have high atomic masses and relatively small atomic radii.

Among the given options:

Zn (Zinc): While it is a transition metal, zinc has a relatively low atomic mass and a larger atomic radius compared to heavier transition metals.
Sc (Scandium): Scandium is a light transition metal, and its density is lower due to its small atomic mass.
La (Lanthanum): Lanthanum is part of the f-block but is usually included as a d-block element. It has a lower density than heavier transition metals.
Os (Osmium): Osmium is a heavy transition metal in the 6th period and has one of the highest atomic masses. It also has a very small atomic radius, leading to the highest density of all naturally occurring elements.
Conclusion:
Osmium (Os) has the highest density of all elements, making it the densest transition metal among the given options. The density of osmium is about 22.59 g/cm³.