Write electron configurations for the following ion: Cd2 Cd2 . Express your answer in order of increasing orbital energy. For example, the electron configuration of LiLi would be entered in complete form as 1s^22s^1 or in condensed form as [He]2s^1.
The Correct Answer and Explanation is :
The electron configuration of Cd²⁺ (cadmium ion with a +2 charge) can be written by first determining the electron configuration of neutral cadmium (Cd), and then accounting for the loss of two electrons due to the +2 charge.
Step 1: Electron Configuration of Neutral Cadmium (Cd)
Neutral cadmium (Cd) has an atomic number of 48, which means it has 48 electrons. The electron configuration for neutral cadmium is:
Cd: [Kr] 4d¹⁰ 5s²
This configuration shows that cadmium’s electrons fill the orbitals in order of increasing energy. The configuration starts with the nearest noble gas, krypton (Kr), followed by the 4d and 5s orbitals.
Step 2: Formation of Cd²⁺
When cadmium forms a Cd²⁺ ion, it loses two electrons. The electrons are typically lost first from the outermost orbitals. For Cd²⁺, the two electrons are removed from the 5s orbital, because the 5s orbital is higher in energy than the 4d orbitals.
Thus, the electron configuration of Cd²⁺ is:
Cd²⁺: [Kr] 4d¹⁰
Explanation:
- [Kr] represents the electron configuration of krypton, the nearest noble gas, which serves as a shorthand to indicate the core electrons (the electrons in complete inner orbitals).
- The 4d¹⁰ part indicates that all ten electrons fill the 4d subshell, which is a relatively stable configuration (since the d orbitals can hold a maximum of ten electrons).
- 5s² was the outermost shell in neutral cadmium, and the two electrons from this orbital are lost to form the Cd²⁺ ion.
Conclusion:
The electron configuration of Cd²⁺ is [Kr] 4d¹⁰, reflecting the removal of two electrons from the 5s orbital, resulting in a stable d-subshell configuration. This ion has a noble gas core (from krypton) and a fully filled 4d subshell.