MCQ
The element with highest ionisation potential is :
- AHydrogen
- BCaesium
- CRadon
- ✓Helium
✓
Answer
Correct option: D.
Helium
(d) Helium
Explanation : When we move from left to right across the periodic table, i.e., from an alkali-metal atom to a noble gas, the n value of the outermost electrons remains the same, but the nuclear charge increases steadily and this increased nuclear attraction requires more energy to remove an electron and as a result the ionisation potential increases along a period. Among the given options Helium and Neon are inert gases and among them, Helium will have the highest ionisation potential as it has the smaller size and higher attraction between nucleus and electrons.
Explanation : When we move from left to right across the periodic table, i.e., from an alkali-metal atom to a noble gas, the n value of the outermost electrons remains the same, but the nuclear charge increases steadily and this increased nuclear attraction requires more energy to remove an electron and as a result the ionisation potential increases along a period. Among the given options Helium and Neon are inert gases and among them, Helium will have the highest ionisation potential as it has the smaller size and higher attraction between nucleus and electrons.
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