In which of the following properties is periodicity not exhibited by the elements ?

Options

A. Atomic radius
B. Atomic weight
C. Ionization energy
D. Electronegativity

Explanation

To solve the question regarding which property does not exhibit periodicity among the given options, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Periodicity**: Periodicity refers to the recurring trends that are observed in the properties of elements as you move across a period or down a group in the periodic table. These trends are largely due to the electronic configuration of the elements.

2. **Evaluate Atomic Radius**:
- **Definition**: The atomic radius is the distance from the nucleus to the outermost shell of electrons.
- **Trend**: As you move from left to right across a period, the atomic radius decreases due to an increase in nuclear charge which pulls the electrons closer to the nucleus. As you move down a group, the atomic radius increases due to the addition of electron shells.
- **Conclusion**: Atomic radius exhibits periodicity.

3. **Evaluate Atomic Weight**:
- **Definition**: Atomic weight is the weighted average mass of an element's isotopes.
- **Trend**: Atomic weight does not show a consistent trend related to the electronic configuration of elements. It does not correlate with the periodic properties.
- **Conclusion**: Atomic weight does not exhibit periodicity.

4. **Evaluate Ionization Energy**:
- **Definition**: Ionization energy is the energy required to remove the most loosely bound electron from an isolated gaseous atom.
- **Trend**: Ionization energy increases across a period due to increasing nuclear charge and decreases down a group due to increased distance of the outermost electron from the nucleus.
- **Conclusion**: Ionization energy exhibits periodicity.

5. **Evaluate Electronegativity**:
- **Definition**: Electronegativity is the tendency of an atom to attract shared pairs of electrons.
- **Trend**: Electronegativity increases across a period and decreases down a group, showing a clear trend related to electronic configuration.
- **Conclusion**: Electronegativity exhibits periodicity.

6. **Final Answer**: Based on the evaluations, the property that does not exhibit periodicity is **atomic weight**.