1. Ionisation potential gradually decreases along a period.
2. In a group of elements, electron affinity decreases as the atomic weight increases.
3. In a given period, electronegativity decreases as the atomic number increases.
Which of these statement (s) is/are correct?
Explanation
Statement 1 is incorrect: Ionization potential (or Energy) increases across a period (left to right) because of increasing nuclear charge, which leads to a stronger attraction between the electrons and the nucleus, making electron removal harder. The effective nuclear charge (Z_eff) increases as protons are added, while shielding remains nearly constant.
Statement 2 is correct: Electron affinity generally becomes less negative down a group. As the atomic size increases, the added electron is farther from the nucleus and experiences greater shielding, reducing the energy released during electron addition. Across a period, electron affinity generally becomes more negative, reflecting stronger attraction to added electrons. Thus, in a group of elements, electron affinity decreases as atomic weight increases.
Statement 3 is incorrect: Electronegativity increases across a period due to increasing nuclear charge, which enhances the ability to attract bonding electrons. However, group-wise, it decreases as atomic size and shielding increase, reducing the effective pull of the nucleus on bonding electrons.