JEE Chemistry 2025 Question with Solution

Given: Four orders of electronegativity are given, and we need to identify the incorrect one.

Find: The incorrect electronegativity order.

Electronegativity generally increases from left to right across a period and decreases down a group.

On the Pauling scale, the relevant values are:

$$\text{Be} = 1.5,\; \text{B} = 2,\; \text{C} = 2.5,\; \text{N} = 3,\; \text{O} = 3.5,\; \text{F} = 4.0$$

Also, between $\text{Mg}$ and $\text{Al}$, the correct order is

$$\text{Mg} < \text{Al}$$

So option $\text{(1)}$ written as

$$\text{Al} < \text{Mg} < \text{B} < \text{N}$$

is incorrect. The correct order should be

$$\text{Mg} < \text{Al} < \text{B} < \text{N}$$

Therefore, the correct option is A.

Given: Electronegativity trend in the periodic table.

Find: Which listed order violates the trend.

1. Option (1): $\text{Al} < \text{Mg} < \text{B} < \text{N}$ This is incorrect because in the same period, electronegativity increases from left to right, so $\text{Mg}$ should be less electronegative than $\text{Al}$. Correct order:

$$\text{Mg} < \text{Al} < \text{B} < \text{N}$$

2. Option (2): $\text{Al} < \text{Si} < \text{C} < \text{N}$ is correct.
3. Option (3): $\text{Mg} < \text{Be} < \text{B} < \text{N}$ is correct.
4. Option (4): $\text{S} < \text{Cl} < \text{O} < \text{F}$ is correct.

Therefore, the incorrect order is Option (1), so the answer is A.