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:
D. A and C Only
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] 4f^ 10 6s^2 Ho (67): [Xe] 4f^ 11 6s^2 Tm (69): [Xe] 4f^ 13 6s^2 Yb (70): [Xe] 4f^ 14 6s^2 Lu (71): [Xe] 4f^ 14 5d^1 6s^2 Hf (72): [Xe] 4f^ 14 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 respectively in their 4f orbitals. Thus, pairs A (Eu and Gd) and C (Yb and Hf) have the same number of electrons in their respective 4f orbitals. Answer: A and C Only
Related: Chemistry — d and f Block Elements · All PYQ Banks