BRAINCAKEBeryllium and Boron
Although there is a general trend in first ionisation energies across a period, and the ionisation energy increases across the period, except from group 2 to group 3.
Boron has a lower ionisation energy than beryllium because outer electron of beryllium is in the 2s sub-shell whilst the outer electron of Boron is in the 2p sub-shell.
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Key terms in this lesson
- 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.
- Sub-shell
- A subdivision of a main energy level (s, p, d or f) made up of orbitals of similar energy.
- Group
- A vertical column of the periodic table, containing elements with the same number of outer-shell electrons.
- Period
- A horizontal row of the periodic table, containing elements with the same number of electron shells.
More in Periodicity
- Ionisation Energy
- Successive Ionisation Energies
- Trends in First Ionisation Energies Across a Period
- Trends in First Ionisation Energies Down a Group
- Nitrogen and Oxygen
- Metallic Bonding
- Properties of Metals
- Giant Covalent Structures
All 14 lessons in Periodicity · All OCR AS-level Chemistry topics