Which is isoelectronic with hydride ion?

Options

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

Explanation

To determine which species is isoelectronic with the hydride ion (H⁻), we need to follow these steps:

### Step 1: Understand the term "isoelectronic"
Isoelectronic species are atoms or ions that have the same number of electrons.

**Hint:** Remember that the number of electrons is determined by the atomic number and any charge on the ion.

### Step 2: Determine the number of electrons in the hydride ion (H⁻)
The hydride ion has gained one electron compared to neutral hydrogen.
- Neutral hydrogen (H) has 1 electron.
- When it gains an electron to form H⁻, it has 2 electrons.

**Hint:** Always account for the charge when determining the number of electrons.

### Step 3: Check the number of electrons in the given options
1. **Helium (He)**:
- Atomic number = 2
- Electrons = 2 (neutral atom)

2. **Lithium ion (Li⁺)**:
- Atomic number = 3
- Neutral lithium has 3 electrons, but as Li⁺, it loses 1 electron, leaving it with 2 electrons.

3. **Hydrogen ion (H⁺)**:
- Atomic number = 1
- Neutral hydrogen has 1 electron, and as H⁺, it loses that electron, leaving it with 0 electrons.

### Step 4: Compare the number of electrons
- H⁻ has 2 electrons.
- He has 2 electrons.
- Li⁺ has 2 electrons.
- H⁺ has 0 electrons.

### Step 5: Identify the isoelectronic species
From the analysis:
- Both Helium (He) and Lithium ion (Li⁺) have 2 electrons, which means they are isoelectronic with the hydride ion (H⁻).

**Conclusion:** The species that is isoelectronic with the hydride ion is both Helium (He) and Lithium ion (Li⁺).

### Final Answer:
Both Helium (He) and Lithium ion (Li⁺) are isoelectronic with the hydride ion (H⁻).

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