Question

Which of the following statement(s) is/are false?
(The question has multiple correct options)
(A) Lanthanum is the first element in Lanthanides
(B) Actinium violates the Aufbau’s Principle
(C) Chromium violates the Pauli’s exclusion principle
(D) Total 10 exchanges are possible for d-electron in Zinc

Answer 1

Hint: Aufbau principle states that the orbital with the lower energy level must be filled first completely, before moving on to the next orbital. While Pauli’s exclusion principle states that no two electrons in the same can have the same or identical values for all 4 of the quantum numbers.

Complete Step-by-Step Solution:
Let us discuss all the options one by one:
1. Lanthanides along with actinides are F -Block elements. Lanthanides consist of a group of elements whose atomic number ranges from 58 to 71. The first element in this series with atomic number 58 is known as Lanthanum. The series of lanthanides gets its name from the first element in the series, i.e. Lanthanum.
2. Aufbau Principle states that once the 7s orbital is filled, the next orbital to start filling is the 4f orbital, and only then we must move on to 6d orbital. But the trend observed in actinium observed is that after the 7s orbital, the 6d orbital gets filled giving it the electronic configuration \[[Rn]6{d^1}7{s^2}\]. Hence Actinium violates the Aufbau’s Principle.
3. The electronic configuration of chromium is \[[Ar]4{s^1}3{d^5}\]. According to the Aufbau principle, the orbital with the lower energy level must be filled first completely, before moving on to the next orbital. 4s orbital is a lower energy orbital as compared to 3d. hence, Chromium violates Aufbau’s Principle.
4. The electronic configuration of zinc is given as \[[Ar]4{s^2}3{d^{10}}\]. Hence the d orbital is completely filled and there cannot be any more exchanges possible with the d orbital.

Hence, the statements A, B, C and are all false statements.

Note: In chromium atom, the electrons are half filled in both the 4s and 3d orbitals. This is because along with fully filled valence orbitals, half-filled valence orbitals are also very stable in comparison to partially filled orbitals.