Fill in the orbital energy diagram for the oxide ion. 2p (5 2s 1s
The Correct Answer and Explanation is:
🧪 Correct Orbital Diagram for O²⁻ (Oxide Ion):
Orbitals (in increasing energy):
makefileCopyEdit1s: ↑↓
2s: ↑↓
2p: ↑↓ ↑↓ ↑↓
- 1s orbital → 2 electrons (↑↓)
- 2s orbital → 2 electrons (↑↓)
- 2p orbitals → 6 electrons (↑↓ ↑↓ ↑↓)
✅ Total electrons = 10
🔍 Explanation
The oxide ion (O²⁻) is formed when a neutral oxygen atom gains two electrons. A neutral oxygen atom (O) has an atomic number of 8, meaning it has 8 electrons. When it gains two more electrons to form O²⁻, it ends up with 10 electrons total, just like a neon (Ne) atom, making it isoelectronic with Ne.
Electrons fill orbitals in order of increasing energy, following the Aufbau principle, Pauli exclusion principle, and Hund’s rule:
- 1s orbital is the lowest in energy and holds 2 electrons (↑↓).
- 2s orbital comes next and holds 2 electrons (↑↓).
- 2p orbitals (px, py, pz) are degenerate (equal in energy). The remaining 6 electrons are placed in these:
- According to Hund’s Rule, each p orbital gets one electron before any gets paired.
- Then the electrons are paired up, completing the 2p subshell: ↑↓ ↑↓ ↑↓.
Thus, the electron configuration of the oxide ion is:
👉 1s² 2s² 2p⁶
This completely fills the n = 2 shell, making O²⁻ a stable ion with a full valence shell, like the noble gas neon.
The orbital diagram represents this electron filling visually, with arrows indicating spin. The stability of O²⁻ comes from its full outer shell, explaining why oxygen tends to gain two electrons in chemical reactions.
