BRAINCAKETrends in First Ionisation Energy Across a Period
First Ionisation energies increase across a period. This is because the nuclear charge is increasing as there are more protons, but the amount of shielding is the same or similar so the atomic radius decreases across a period.
Shielding refers to the repulsion of the electron to be removed by the electrons in the inner shells.
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Key terms in this lesson
- Atomic orbital
- A region in space around the nucleus where there is a 95% probability of finding an electron of a given energy.
- 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.
- Atomic radius
- A measure of the size of an atom, found by measuring the distance between two adjacent nuclei and dividing by two.
- 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 Atomic Structure
- Quantum Mechanics
- Energy Levels
- Atomic Orbitals
- Order of filling orbitals
- Electron Configuration
- First Ionisation Energy
- Successive Ionisation Energies
- Trends in Ionisation Energy Down A Group
All 22 lessons in Atomic Structure · All AQA AS-level Chemistry topics