The number of `pi` electrons required for a planar cyclic conjugated system to exhibit aromatic behaviour is `(4n+2)`. Here n is

Options

A. number of C atoms in the system
B. number of `pi` bonds
C. a non - negative integer
D. number of bonds in the system.

Answer

To solve the question regarding the number of π electrons required for a planar cyclic conjugated system to exhibit aromatic behavior, we need to understand Huckel's rule, which states that a compound is aromatic if it contains \(4n + 2\) π electrons, where \(n\) is a non-negative integer.

### Step-by-Step Solution:

1. **Understanding Huckel's Rule**:
- Huckel's rule is a criterion for aromaticity, which states that a cyclic, planar molecule with a conjugated system of π electrons will be aromatic if it has \(4n + 2\) π electrons.
- Here, \(n\) is an integer that can take values like 0, 1, 2, etc.

2. **Identifying the Options**:
- The options provided are:
a) Number of C atoms in the system
b) Number of π bonds
c) A non-negative integer
d) Number of bonds in the system

3. **Analyzing Each Option**:
- **Option a (Number of C atoms in the system)**: This is incorrect because the number of carbon atoms does not directly determine the value of \(n\).
- **Option b (Number of π bonds)**: This is also incorrect as \(n\) does not correspond to the number of π bonds.
- **Option c (A non-negative integer)**: This is the correct answer because \(n\) is defined as a non-negative integer in Huckel's rule.
- **Option d (Number of bonds in the system)**: This is incorrect as well since the number of bonds does not define \(n\).

4. **Conclusion**:
- Therefore, the correct answer is that \(n\) is a non-negative integer.

### Final Answer:
**n is a non-negative integer.**