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
- Ion
- A positively or negatively charged atom or group of atoms, formed by the loss or gain of electrons.
- Ionisation
- The loss or gain of electrons by an atom or molecule to form a charged ion.
- Electron shell
- A main energy level occupied by electrons, given a principal quantum number n, with n = 1 closest to and lowest in energy relative to the nucleus.
- First ionisation energy
- The energy needed to remove one electron from each atom of one mole of atoms in their gaseous state to form one mole of gaseous +1 ions, under standard conditions.
- 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.
More in Atoms, Ions and Compounds
- Calculating Relative Atomic Mass
- Chemical Formulae
- Polyatomic ions
- Chemical Equations
- Electron Shells
- Spin
- Ionisation Energy
- Trends in Ionisation Energy
All 17 lessons in Atoms, Ions and Compounds · All OCR AS-level Chemistry topics