The cation having the largest size in the periodic table is

Options

A. `Ba^(+2 )`
B. `Ca^(+2)`
C. `Cs^+ `
D. `Fe^(+3)`

Answer

To determine the cation with the largest size in the periodic table, we can follow these steps:

### Step 1: Understand the Concept of Cation Size
Cations are positively charged ions formed when an atom loses one or more electrons. The size of a cation is generally smaller than its parent atom due to the loss of electrons, which results in a decrease in electron-electron repulsion and a greater effective nuclear charge acting on the remaining electrons.

**Hint:** Remember that cations are smaller than their neutral atoms due to the loss of electrons.

### Step 2: Identify Relevant Cations
We need to compare cations from different groups and periods. For this question, we will focus on cations from the 4th, 5th, and 6th periods, particularly those formed from alkali and alkaline earth metals.

**Hint:** Look at the periodic table and note the positions of alkali and alkaline earth metals.

### Step 3: Compare Cations from Different Periods
- **Cations from the 4th Period:**
- Sodium (Na⁺), Potassium (K⁺), Calcium (Ca²⁺)

- **Cations from the 5th Period:**
- Rubidium (Rb⁺), Strontium (Sr²⁺)

- **Cations from the 6th Period:**
- Cesium (Cs⁺), Barium (Ba²⁺)

**Hint:** Consider the trend in size as you move down the groups in the periodic table.

### Step 4: Analyze the Charge Effect
- Cations with a higher positive charge (like Ba²⁺) will generally be smaller than those with a lower positive charge (like Cs⁺) because the greater positive charge pulls the remaining electrons closer to the nucleus.

**Hint:** Remember that a cation with a +1 charge will be larger than a cation with a +2 charge from the same element.

### Step 5: Compare the Sizes of Relevant Cations
- **Cesium (Cs) vs. Barium (Ba):**
- Cs is larger than Ba as a neutral atom.
- Cs⁺ (loses one electron) will be larger than Ba²⁺ (loses two electrons).

### Conclusion
After comparing the sizes of the cations, we find that Cs⁺ is larger than Ba²⁺. Therefore, the cation with the largest size in the periodic table is **Cs⁺ (Cesium ion)**.

**Final Answer:** The cation having the largest size in the periodic table is Cs⁺ (Cesium ion).

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