Question

The element with the least melting point in $VIA$ the group is:
(A) $O$
(B) $S$
(C) $Se$
(D) $Te$

Answer 1

The melting point of the element is defined as the temperature at which the solid and liquid forms are in equilibrium. The element with the least melting point will have the least temperature. The melting point of elements also depends on the intermolecular forces acting on them. Some of the forces like weak forces, Vander wall’s forces.

Complete step by step answer:
First, we will understand the physical properties such as melting point and boiling point. The groups and periods of the periodic table also follow basic trends of these physical properties. The physical properties like melting point and boiling point depend on one of the forces that are Vander wall’s forces. So, first, we will try to understand the Vander wall’s forces. The Vander wall’s forces are defined as the intermolecular forces which are responsible for the attraction between the molecules. It is known that the Vander wall’s forces are directly proportional to the molecular mass of the element. Now we will compare the molecular mass of the given element. The element with the least molecular mass will have the least Van Der wall’s forces. So now we will write the molecular mass of the elements in the given options. So, the molecular masses are as follows $O \to 16,S \to 32,Se \to 79,Te \to 127$
Now we can conclude that the element oxygen has the least molecular mass so it will have the least Van Der wall’s forces. So, the order of melting point based on Vander wall’s forces is given $O < S < Se < Te$ . Therefore, the element with the least melting point will be oxygen.
Therefore, the correct option is (A).

Note:
According to the position of elements in the periodic table the elements are in a group in the order $O,S,Se,Te$ from top to bottom. According to the trend, the melting point increases down the group. Therefore, the element of oxygen has the least melting point.