Atom size trends
The best way to understand atom size trends is by adding electrons, protons, and neutrons to an atom one by one to see how they affect atom size. You will learn why atom size gradually decreases from left to right across any given row in the periodic table, and increases again when you continue on to the next row.
This lesson is a part of MEL Chemistry VR. Learn more →
atoms, atomic structure, electrons, protons, atom size, atomic radius, coulombic force
- Revise the elements that are arranged in the Periodic Table according to their atomic number: number of protons (equal to the number of electrons).
- Learn that protons attract electrons, but electrons themselves repel.
- Learn that atomic size decreases through the periods.
- Learn that atomic size increases through the group.
- Find the largest and the smallest atoms in the table.
History and sources of knowledge
- Experiments to measure the atom size: Rayleigh experiment with oil.
- Modern methods: x-ray and spectroscopy.
Topics to discuss
- Atom sizes: definition, problems of measurement. (Revise VR lesson ’Atom size’)
- Counterintuitive trends in periods: the atoms became heavier but atomic size decreases.
- Forces determining the size of atoms.
- Periodicity in atomic size.
- Why the atom size decreases in periods?
- Why the atom size increases in groups?