Pairs of elements with the same number of electrons in their respective 4f orbital are [Atomic number. Eu-63, Gd-64, Dy-66, Ho-67, Tm-69, Yb-70, Lu-71, Hf-72] A. (Eu and Gd) B. (Dy and Ho) C. (Yb and Hf) D. (Lu and Tm) Choose the correct answer from the options given below:

Step-by-step solution

The electronic configurations of the given elements are: Eu (63): [Xe] 4f^7 6s^2 Gd (64): [Xe] 4f^7 5d^1 6s^2 Dy (66): [Xe] 4f¹⁰ 6s^2 Ho (67): [Xe] 4f¹¹ 6s^2 Tm (69): [Xe] 4f¹³ 6s^2 Yb (70): [Xe] 4f¹⁴ 6s^2 Lu (71): [Xe] 4f¹⁴ 5d^1 6s^2 Hf (72): [Xe] 4f¹⁴ 5d^2 6s^2 From the above configurations: Eu and Gd both have 7 electrons in their 4f orbitals. Yb and Hf both have 14 electrons in their 4f orbitals. Dy and Ho have 10 and 11 electrons respectively in their 4f orbitals. Lu and Tm have 14 and 13 electrons respectivel