Chemistry - GENERAL CHEMISTRY Question with Solution | TestHub

(A) Lanthanum is the first element of lanthanides

• Incorrect because lanthanides generally start from Cerium (Ce, Z=58); La is often placed separately as an f-block element.

(B) Actinium violates Aufbau’s principle

• Correct. Ac has configuration $[Rn]6d^{1}7s^2$, showing deviation from expected filling.

(C) Chromium violates Pauli’s exclusion principle

Cr = $[Ar]3d^{5}4s^1$

Incorrect. Cr violates the Aufbau principle, not Pauli's principle.

(D) Total 10 exchange energies are possible for d-electrons in Zn

but exchange energy requires parallel spin electrons in different orbitals, and Zn has no unpaired electrons.

• Zn: $[Ar]3d^{10}4s^2$. Since all d-orbitals are completely filled, there are no exchange pairs.

Correct false statements: A, C, D