The number of 4f electrons in the ground state electronic configuration of Gd is ______. [Atomic num — d and f Block Elements Chemistry Question

💡 Solution & Explanation

**Step 1: Identify the atomic number and ionization state** Gadolinium (Gd) has atomic number 64, and we need the Gd²⁺ ion (2+ charge). **Step 2: Write the ground state configuration of neutral Gd (Z = 64)** Gd: [Xe] 4f⁷ 5d¹ 6s² This accounts for 54 (Xe) + 7 + 1 + 2 = 64 electrons. **Step 3: Remove electrons to form Gd²⁺** When forming a 2+ ion, remove 2 electrons. Electrons are removed from the outermost orbitals first (6s orbital before 5d). Gd²⁺: [Xe] 4f⁷ 5d¹ **Step 4: Count the 4f electrons** In the Gd²⁺ configuration, the 4f subshell contains **7 electrons**. Therefore, the answer is **7.00**.