Which of the following properties displays progressive increase with the rise in atomic number across a period in the periodic table?

Options

A. Size of the atom
B. Electronegativity
C. Ionization potential
D. Electron affinity

Answer

To determine which property displays a progressive increase with the rise in atomic number across a period in the periodic table, we will analyze each of the given options step by step.

### Step 1: Analyze Atomic Size
- **Concept**: Atomic size generally decreases as you move from left to right across a period due to the increase in effective nuclear charge, which pulls the electrons closer to the nucleus.
- **Conclusion**: Therefore, atomic size does not display a progressive increase. **(Not Correct)**

### Step 2: Analyze Electronegativity
- **Concept**: Electronegativity is the ability of an atom to attract electrons from other atoms. As we move across a period from left to right, the effective nuclear charge increases, which enhances the ability of an atom to attract electrons.
- **Example**: For elements like carbon, nitrogen, oxygen, and fluorine, electronegativity increases.
- **Conclusion**: Electronegativity displays a progressive increase across a period. **(Correct)**

### Step 3: Analyze Ionization Potential
- **Concept**: Ionization potential (or ionization energy) is the energy required to remove the outermost electron from an atom. As we move across a period, the ionization potential generally increases due to the increasing effective nuclear charge, making it more difficult to remove an electron.
- **Conclusion**: Ionization potential does not display a progressive increase; it actually increases. **(Not Correct)**

### Step 4: Analyze Electron Affinity
- **Concept**: Electron affinity is the energy change when an electron is added to a neutral atom to form a negative ion. While electron affinity generally increases across a period, it does not do so uniformly. For example, nitrogen has a lower electron affinity than expected due to its half-filled p-orbital stability.
- **Conclusion**: Electron affinity does not display a continuous progressive increase. **(Not Correct)**

### Final Answer
Based on the analysis, the property that displays a progressive increase with the rise in atomic number across a period is **Electronegativity**.

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