Which one of the following ions has the highest value of ionic radius?

Options

A. `Li^(+)`
B. `B^(3+)`
C. `O^(2-)`
D. `F^(-)`

Answer

To determine which ion has the highest ionic radius among the given options, we can follow these steps:

### Step 1: Identify the Ions
Let's identify the ions we are comparing. The ions mentioned in the video are:
- Lithium ion (Li⁺)
- Boron ion (B³⁺)
- Oxide ion (O²⁻)
- Fluoride ion (F⁻)

### Step 2: Determine the Number of Electrons
Next, we need to find the number of electrons in each ion:
- **Li⁺**: Lithium has an atomic number of 3, so it has 3 electrons. When it loses one electron to become Li⁺, it has 2 electrons.
- **B³⁺**: Boron has an atomic number of 5, so it has 5 electrons. When it loses three electrons to become B³⁺, it has 2 electrons.
- **O²⁻**: Oxygen has an atomic number of 8, so it has 8 electrons. When it gains two electrons to become O²⁻, it has 10 electrons.
- **F⁻**: Fluorine has an atomic number of 9, so it has 9 electrons. When it gains one electron to become F⁻, it has 10 electrons.

### Step 3: Determine the Electronic Configuration
Now, let's write the electronic configurations for these ions:
- **Li⁺**: The electronic configuration is 1s².
- **B³⁺**: The electronic configuration is also 1s².
- **O²⁻**: The electronic configuration is 1s² 2s² 2p⁶ (10 electrons).
- **F⁻**: The electronic configuration is also 1s² 2s² 2p⁶ (10 electrons).

### Step 4: Compare Ionic Sizes
Now we need to compare the ionic sizes:
- **Li⁺ and B³⁺** both have 2 electrons and the same electronic configuration (1s²). They are isoelectronic with each other but Li⁺ is smaller due to having a higher nuclear charge.
- **O²⁻ and F⁻** both have 10 electrons and the same electronic configuration (1s² 2s² 2p⁶). However, O²⁻ has a lower nuclear charge than F⁻, making it larger.

### Step 5: Conclusion
From the comparison, we can conclude that:
- Li⁺ and B³⁺ are smaller than both O²⁻ and F⁻.
- Between O²⁻ and F⁻, O²⁻ is larger due to having a lower nuclear charge.

Thus, the ion with the highest ionic radius is **O²⁻**.

### Final Answer:
**O²⁻ has the highest value of ionic radius.**

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