Summary
The Periodic Table organizes elements based on their atomic number, electron configuration, and recurring chemical properties. It helps predict the properties of elements and their compounds.
- Electron Configuration — the arrangement of electrons in an atom's orbitals. Example: Carbon has an electron configuration of 1s2 2s2 2p2.
- Ionisation Energy — the energy required to remove an electron from an atom. Example: The first ionisation energy of hydrogen is the energy needed to remove its single electron.
- Atomic Radius — half the distance between the nuclei of two adjacent atoms. Example: The atomic radius decreases across a period and increases down a group.
- Periodic Trends — patterns in the periodic table that show variations in element properties. Example: Ionisation energy generally increases across a period and decreases down a group.
Exam Tips
Key Definitions to Remember
- Electron Configuration
- Ionisation Energy
- Atomic Radius
- Periodic Trends
Common Confusions
- Confusing atomic radius with ionic radius
- Misunderstanding the order of filling electron orbitals
Typical Exam Questions
- What is the electron configuration of oxygen? Answer: 1s2 2s2 2p4
- How does ionisation energy change across a period? Answer: It generally increases.
- Why does atomic radius decrease across a period? Answer: Due to increased nuclear charge attracting electrons closer.
What Examiners Usually Test
- Understanding of electron configurations and their notation
- Ability to explain trends in ionisation energy and atomic radius
- Application of periodic trends to predict element properties