Question

The decreasing order of atomic radii (pm) of \( \text{Li}, \, \text{Be}, \, \text{B}, \, \text{C} \) is:

• A. Be > Li > B > C
• B. Li > Be > B > C
• C. C > B > Be > Li
• D. Li > C > Be > B

Answer 1

The Correct Option is B

The question asks about the decreasing order of atomic radii for the elements \( \text{Li} \), \( \text{Be} \), \( \text{B} \), and \( \text{C} \). To solve this, we need to understand the periodic trend of atomic radii. 

In the periodic table, as we move from left to right across a period, the atomic radius generally decreases. This is because, with the addition of each proton and electron, the increased nuclear charge pulls the electron cloud closer to the nucleus, reducing the size of the atom.

For the given elements, they belong to the second period of the periodic table:

1. Lithium (\( \text{Li} \))
2. Beryllium (\( \text{Be} \))
3. Boron (\( \text{B} \))
4. Carbon (\( \text{C} \))

Based on the periodic trend, the atomic radii decrease as follows: \( \text{Li} > \text{Be} > \text{B} > \text{C} \).

Let's justify this by ruling out the other options:

Be > Li > B > C

• : Incorrect because \(\text{Li}\) should be greater than \(\text{Be}\) as it is further left in the periodic table.

Li > C > Be > B

• : Incorrect because \(\text{C}\) should not be greater than \(\text{Be}\) and \(\text{B}\).

C > B > Be > Li

• : Incorrect because carbon actually has the smallest atomic radius among these elements.

Thus, the correct order is:

Li > Be > B > C

, which matches the option given as the correct answer.

 

This understanding of periodic trends is crucial for questions involving atomic properties in government exams.