Question

Ionisation potential values of d-block elements as compared to the potential value of f-block elements are
A) Higher
B) Equal
C) Lower
D) All of these

Answer 1

Hint: Ionisation potential is also known as ionisation enthalpy. It is best described as the amount of energy that is required to remove an electron. It increases with the increase in the nuclear charge.

Complete Step by Step Solution:
Ionisation energy or ionisation enthalpy is described as the total amount of energy that is required to remove an electron from the ground state of the isolated gaseous atom.
Since to remove an electron from the atom there is always energy required, the ionisation potential will always be positive. The ionisation energy will always increase from left to right in the periodic table due to an increase in the nuclear charge.
The increase in the nuclear charge will be balanced by the shielding effect to some extent, however, the amount of increase in the ionisation potential due to this effect will still be very minimal. The ionisation energy of the first 5d elements is much greater as compared to those of 3d and 4d elements.
The ionisation potential is gradually decreased in the f- block elements due to a decrease in the shielding effect in the elements. It is because the space that has been occupied by the 6s and the 7s orbitals is much larger as compared to the space that is occupied by 4s and 5s orbitals. Because of this, the 6s and 7s orbitals are not penetrated properly by their nuclei and so the f-block elements hold the electron in their outermost shell very weakly.
Hence option A is the correct answer

Note: Ionisation energy of the elements is directly proportional to electronegativity. If there is less electronegativity there will also be less ionisation energy. For metals, it will be easier for them to lose electrons as their motive will be to obtain a full outer shell, so metals will be more reactive as they require less energy to have a full outer shell. For non-metals, it would be easier to gain electrons. The reactivity of an element is also directly proportional to the electronegativity and ionisation energy of the element.