Question

Which transition metal has the highest density?
A) $\text{ Zn }$
B) $\text{ Sc }$
C) $\text{ La }$
D) $\text{ Os }$

Answer 1

Hint: The density is a mass of an object per unit volume. The mass of an element is concentrated in the nucleus. Transition elements which have high atomic mass and less volume are highly dense.
$\text{ Density = }\dfrac{\text{Mass }}{\text{Volume}}\text{ }$

Complete Solution :
Density is an intensive property and it is used to determine the element and material. Density is a measure of the amount of matter present in the substance. It is defined as the mass of an object per unit volume. The relation is written as:
$\text{ Density = }\dfrac{\text{Mass }}{\text{Volume}}\text{ }$

- The transition metal is those which have partially filled d-orbital. The size of transition metal decreases as we move from left to right but the atomic number and atomic mass of a transition metal go on increasing. Due to the increase in atomic number the transition metal has a higher charge. Therefore transition metals have a higher charge to radius ratio.
- In other words, the spread of elements goes on decreasing and thus transition elements have lower volume and higher mass. The density is directly related to mass and inversely related to the volume. Thus transition elements have high density.
- The osmium is a transition metal . It has the highest density of $\,\text{22}\text{.59 g/c}{{\text{m}}^{\text{3}}}\text{ }$ at room temperature. The osmium has a higher density than any naturally occurring element and also the highest density of any element radioactivity element. It is the densest element because most of the mass is converted in the smallest amount of space.
So, the correct answer is “Option D”.

Note: Note that the elements which are at the top of the periodic table are low dense elements. The iridium is also a dense element only at room temperature above the pressure of $\text{ 2}\text{.98 GPa }$ but osmium is highly dense at all temperatures.