BRAINCAKESuccessive Ionisation Energies
The first ionisation energy is the least endothermic as energy is needed to remove an electron from a neutral atom. In a +1 ion, the proton:electron ratio is increased. The same number of protons are attracting fewer electrons and the effective nuclear charge is increased.
The second ionisation energy is therefore more endothermic than the first as more energy is needed to remove and electron from a +1 ion. The third electron needs even more energy than the second, and so on.
A large jump in successive ionisation energies occurs when an electron is being removed from a shell closer to the nucleus. For example,
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Key terms in this lesson
- First ionisation energy
- The enthalpy change when each atom in one mole of gaseous atoms loses one electron to form one mole of gaseous 1+ ions.
- Second ionisation energy
- The energy needed to remove one electron from each ion of one mole of gaseous 1+ ions to form one mole of gaseous 2+ ions, under standard conditions.
- Endothermic
- Describes a reaction in which energy is transferred from the surroundings to the system, so the enthalpy change is positive.
- Period
- A horizontal row of the periodic table, containing elements with the same number of electron shells.
More in Atomic Structure
- Quantum Mechanics
- Energy Levels
- Atomic Orbitals
- Order of filling orbitals
- Electron Configuration
- First Ionisation Energy
- Trends in First Ionisation Energy Across a Period
- Trends in Ionisation Energy Down A Group
All 22 lessons in Atomic Structure · All AQA AS-level Chemistry topics