Give the electron configurations for the following ions: P5+, P3-, Sn4+, Se2-, I-, and Ni2+. 2.10 Potassium iodide (KI) exhibits predominantly ionic bonding. The K+ and I– ions have electron structures that are identical to which two inert gases? 2. With regard to electron configuration, what do all the elements in Group IIA of the periodic table have in common?
The Correct Answer and Explanation is :
1. Electron Configurations for Ions:
- P⁵⁺: The electron configuration of a neutral phosphorus (P) atom is 1s² 2s² 2p⁶ 3s² 3p³. The P⁵⁺ ion has lost five electrons, so the electron configuration becomes:
- P⁵⁺: 1s² 2s² 2p⁶
- P³⁻: A neutral phosphorus (P) atom has 15 electrons. The P³⁻ ion has gained three electrons, so the electron configuration becomes:
- P³⁻: 1s² 2s² 2p⁶ 3s² 3p⁶ (which is the same as Argon)
- Sn⁴⁺: The neutral tin (Sn) atom has the electron configuration [Kr] 4d¹⁰ 5s² 5p². The Sn⁴⁺ ion has lost four electrons, so its electron configuration becomes:
- Sn⁴⁺: [Kr] 4d¹⁰
- Se²⁻: The neutral selenium (Se) atom has the electron configuration [Ar] 3d¹⁰ 4s² 4p⁴. The Se²⁻ ion has gained two electrons, so its electron configuration becomes:
- Se²⁻: [Ar] 3d¹⁰ 4s² 4p⁶ (which is the same as Krypton)
- I⁻: The neutral iodine (I) atom has the electron configuration [Kr] 4d¹⁰ 5s² 5p⁵. The I⁻ ion has gained one electron, so its electron configuration becomes:
- I⁻: [Kr] 4d¹⁰ 5s² 5p⁶ (which is the same as Xenon)
- Ni²⁺: The neutral nickel (Ni) atom has the electron configuration [Ar] 3d⁸ 4s². The Ni²⁺ ion has lost two electrons, so its electron configuration becomes:
- Ni²⁺: [Ar] 3d⁸
2. Potassium Iodide (KI) and Inert Gases:
In potassium iodide (KI), K⁺ and I⁻ ions exhibit the electron configuration of Argon (Ar) and Xenon (Xe), respectively.
- K⁺ (Potassium ion): The electron configuration of the neutral potassium (K) atom is [Ar] 4s¹. When it loses one electron, it attains the electron configuration of Argon (Ar), which is [Ar] 3d¹⁰ 4s².
- I⁻ (Iodide ion): The electron configuration of a neutral iodine (I) atom is [Kr] 4d¹⁰ 5s² 5p⁵. When it gains one electron, it attains the electron configuration of Xenon (Xe), which is [Kr] 4d¹⁰ 5s² 5p⁶.
3. Electron Configuration of Group IIA Elements:
Group IIA elements (alkaline earth metals) share the common characteristic of having two electrons in their outermost (valence) shell. These elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
- The electron configurations of these elements typically end in s² for their outermost shell. For example:
- Be: 1s² 2s²
- Mg: 1s² 2s² 2p⁶ 3s²
- Ca: 1s² 2s² 2p⁶ 3s² 3p⁶ 4s²
Thus, all elements in Group IIA have their valence electrons in the s orbital of the outermost shell, with two electrons. This configuration leads to the formation of 2+ ions when they lose these two outermost electrons during chemical reactions. These properties help characterize the alkaline earth metals as being less reactive than alkali metals, but still reactive enough to form stable ionic compounds.