Identify whether the given statements about ionisation energy are correct or incorrect.
Statement A: The ionisation energy of an atom is the amount of energy that is required to remove an electron from a mole of atoms in the gas phase.
Statement B: The ionisation energy increases from top to bottom in groups and decreases from left to right across a period.
Show answer & explanation
Correct answer: B
Explanation
The correct answer is option 2 i.e. Only Statement A is correct.
- Statement A is correct. The ionization energy of an atom is indeed the amount of energy required to remove an electron from a mole of atoms in the gas phase.
- Statement B is incorrect. Ionization energy generally decreases from top to bottom in groups because additional electron shells are added, increasing atomic size and reducing the attraction between the nucleus and the outer electrons. Conversely, ionization energy increases from left to right across a period due to the increasing nuclear charge, which attracts electrons more strongly.