Question

In group 17, which property does not follow the regular trend?

• A. Electron affinity
• B. Ionisation energy
• C. Covalent radii
• D. Ionic radii

Hint:

Keep in mind that certain properties such as electron affinity can show irregular trends due to specific atomic characteristics like size and electron-electron repulsion.

Answer 1

The Correct Option is A

Within group 17 (halogens) of the periodic table, most properties exhibit a consistent trend downwards. However, electron affinity deviates from this regularity. While electron affinity generally increases across a period, it does not increase uniformly down group 17. Specifically, fluorine's electron affinity is lower than chlorine's. This anomaly is attributed to fluorine's smaller atomic size, which leads to electron repulsion within its valence shell. In contrast, ionization energy consistently decreases down the group, covalent radii increase due to the addition of electron shells, and ionic radii also increase regularly with more electron shells. Therefore, electron affinity is the property that does not follow the typical trend in group 17.