Which of the following has the lowest ionisation potential?

Options

A. `3d^(2)`
B. `4s^(1)`
C. `2p^(6)`
D. `3p^(5)`

Explanation

To determine which of the given options has the lowest ionization potential, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Ionization Potential**:
- Ionization potential (or ionization energy) is the minimum energy required to remove an electron from the outermost shell of an atom.

2. **Trends in Ionization Potential**:
- Ionization potential decreases down a group in the periodic table. This is because as you move down a group, the atomic size increases due to the addition of electron shells, making it easier to remove the outermost electron.
- Conversely, ionization potential increases from left to right across a period. This is due to the increase in nuclear charge, which holds the electrons more tightly.

3. **Identify the Group and Period**:
- If the options provided include elements from different groups, we need to identify which group has the lowest ionization potential.
- S-block elements (alkali metals) generally have the lowest ionization potentials due to their larger atomic size.

4. **Evaluate the Options**:
- Compare the elements in the options based on their group and period. Alkali metals (Group 1) will usually have the lowest ionization potential.

5. **Select the Correct Option**:
- Based on the analysis, if one of the options is an alkali metal, it will have the lowest ionization potential. In the provided transcript, it was mentioned that option B corresponds to an element with the configuration 4s1, indicating it is likely an alkali metal.

### Final Answer:
- Therefore, the element corresponding to option B has the lowest ionization potential.

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