Which of the property of alkali metals is not listed correctly ?

Options

A. The least electronegative metal: Cs
B. A natural radioactive metal: Fr
C. The alkali metal the lowest density: K
D. The most abundant alkali metal in the earth's crush: Na

Explanation

To determine which property of alkali metals is not listed correctly, we will analyze each option provided in the question step by step.

### Step 1: Analyze the first statement
**Statement:** "The least electronegativity of cesium."
- **Explanation:** Alkali metals have low electronegativity values, and as we move down the group from lithium to cesium, the electronegativity decreases. Cesium, being the heaviest alkali metal, indeed has the least electronegativity among them.
- **Conclusion:** This statement is true.

### Step 2: Analyze the second statement
**Statement:** "A natural radioactive metal is francium."
- **Explanation:** Francium is indeed a member of the alkali metal group and is known to be highly radioactive. It is found in trace amounts in nature and is the least stable of the first 101 elements on the periodic table.
- **Conclusion:** This statement is true.

### Step 3: Analyze the third statement
**Statement:** "The alkali metal with the lowest density is potassium."
- **Explanation:** The densities of alkali metals generally decrease as we move down the group. Lithium has the lowest density, followed by sodium, and then potassium. Cesium, being the heaviest, has a higher density than potassium. Therefore, potassium does not have the lowest density; lithium does.
- **Conclusion:** This statement is false or not listed correctly.

### Step 4: Analyze the fourth statement
**Statement:** "The most abundant alkali metal in the Earth's crust is sodium."
- **Explanation:** Sodium is indeed the most abundant alkali metal found in the Earth's crust, primarily in the form of sodium chloride (table salt) and other minerals.
- **Conclusion:** This statement is true.

### Final Conclusion
After analyzing all the statements, the only property that is not listed correctly is the third statement: "The alkali metal with the lowest density is potassium." The correct statement should be that lithium has the lowest density among alkali metals.

### Summary of the Solution
- The first statement is true.
- The second statement is true.
- The third statement is false (the correct alkali metal with the lowest density is lithium).
- The fourth statement is true.

Thus, the answer to the question is that the third option is not listed correctly.

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