among the alkali metals caesium is the most reactive because

Options

A. It has incomplete shell which is nearest to the nucleus
B. It has a single electron it the valence shell
C. It is the heaviest alklali metal
D. The outermost electron is more loosely bound than the outermost electron of the other alkali metals

Answer

**Step-by-Step Solution:**

1. **Understanding Alkali Metals**: Alkali metals include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), and cesium (Cs). They are known for their tendency to lose one electron from their outermost shell to form positive ions.

2. **Electron Configuration**: The electron configurations of alkali metals show that as we move down the group from Li to Cs, the number of electron shells increases. For example:
- Lithium (Li): 2, 1
- Sodium (Na): 2, 8, 1
- Potassium (K): 2, 8, 8, 1
- Rubidium (Rb): 2, 8, 18, 8, 1
- Cesium (Cs): 2, 8, 18, 18, 8, 1

3. **Distance of Valence Electron**: The outermost electron in cesium is located in the fifth shell, making it further away from the nucleus compared to the outermost electrons of the other alkali metals.

4. **Nuclear Attraction**: The increased distance of the valence electron from the nucleus results in a weaker force of attraction between the nucleus and the outermost electron. This makes it easier for cesium to lose its outermost electron compared to the other alkali metals.

5. **Reactivity**: Because cesium can lose its outermost electron more easily due to the reduced nuclear attraction, it is the most reactive among the alkali metals.

6. **Conclusion**: Therefore, cesium is the most reactive alkali metal due to its larger atomic size, which leads to a weaker attraction between the nucleus and the valence electron.

**Final Answer**: Cesium is the most reactive alkali metal because its outermost electron is further away from the nucleus, resulting in a weaker attraction and making it easier to lose that electron.

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