Hydride ions is isoelectronic with

Options

A. `He^(+)`
B. `H^(+)`
C. `Be^(+)`
D. He

Answer

To determine which ion is isoelectronic with the hydride ion (H⁻), we need to analyze the electron configuration of the hydride ion and compare it with the options given.

### Step-by-Step Solution:

1. **Identify the Hydride Ion (H⁻)**:
- The hydride ion (H⁻) is formed when a hydrogen atom gains an extra electron.
- Hydrogen (H) has an atomic number of 1, meaning it has 1 proton and normally 1 electron.
- When it gains an electron, the hydride ion (H⁻) has a total of 2 electrons.

2. **Determine the Electron Configuration**:
- The electron configuration for H⁻ is simply 1s², as it has 2 electrons occupying the 1s orbital.

3. **Analyze the Options**:
- **Option 1: Helium ion (He⁺)**:
- Helium has an atomic number of 2, which means it has 2 protons and normally 2 electrons.
- He⁺ means it has lost one electron, so it has 1 electron left (1s¹).
- **Option 2: Hydrogen ion (H⁺)**:
- H⁺ means it has lost its only electron, so it has 0 electrons.
- **Option 3: Beryllium ion (Be⁺)**:
- Beryllium has an atomic number of 4, which means it has 4 protons and normally 4 electrons.
- Be⁺ means it has lost one electron, so it has 3 electrons (1s² 2s¹).
- **Option 4: Helium (He)**:
- Helium has 2 electrons (1s²).

4. **Compare Electron Counts**:
- H⁻ has 2 electrons (1s²).
- He⁺ has 1 electron (1s¹).
- H⁺ has 0 electrons.
- Be⁺ has 3 electrons (1s² 2s¹).
- He has 2 electrons (1s²).

5. **Conclusion**:
- The hydride ion (H⁻) is isoelectronic with helium (He), as both have the same number of electrons (2 electrons).

### Final Answer:
The hydride ion (H⁻) is isoelectronic with **helium (He)**.

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