Which trend is followed by ionisation energy across a period?
- Continuously increases
- Generally increases with some dips
- Continuously decreases
- Has no clear pattern in the standard view
Show answer and solution
Correct answer: B. Generally increases with some dips
1. Ionisation energy rises with nuclear charge across a period.
2. There are exceptions where the configuration is especially stable.
3. Group 13 dips below Group 2; Group 16 dips below Group 15.
4. So the trend is rising overall with small dips at known positions.
5. Hence the general statement 'increases with some dips' is correct.
_Source: syllabus Science Ch 5 'Periodic Classification of Elements'_