Question

In general, the property (magnitudes only) that shows an opposite trend in comparison to other properties across a period is;
(A) Ionisation enthalpy
(B) Electronegativity
(C) Atomic radius
(D) Electron gain enthalpy

Answer 1

Hint: When we move across the periodic table, there will be a decrease in the radius of the electron. The other entities like electronegativity, electron gain enthalpy, and ionisation enthalpy depend upon the outer shell configuration and also the size of the atomic radius.

Complete Step by Step Solution:
Ionisation enthalpy is defined as the amount of energy that is required to remove an electron from an atom that is in the gaseous state. The ionisation enthalpy depends upon the factors such as the penetration effect, shielding effect, and the electronic configuration of the atom.
Electronegativity is a dimensionless property and it is defined as the tendency of an electron by which it attracts a shared pair of electrons towards itself. When we move across a periodic table the nuclear charge will increase whereas the atomic radius will decrease.

Electron gain enthalpy is defined as the change in the enthalpy that is associated with a gaseous atom that has been isolated when it gains an atom which leads to the formation of its corresponding anion.

Ionisation energy, electron gain enthalpy, and electronegativity will increase as we move across the periodic table but the atomic radius will decrease.
Hence, option C is the correct answer

Note: The atoms of the periodic table are arranged in such a manner that when we move across the table the size of the atom will increase. All of the elements in the periodic table prefer an octet formation and will try to form a stable electronic configuration. By analysing the properties mentioned above, the physical, chemical and mechanical properties of the elements can be predicted.