About the Atomic Radius

The atomic radius of an element is a measurement of how close two atoms are to each other. It can be measured in different ways, such as using covalent bonds or Van der Waals bonds, and is often measured in pirometers (picometres) or angstroms.

Typical Trends in Atomic Radius

There are a few periodic trends in atomic radius that are common across most elements on the periodic table. These trends make it easier to understand the size of atoms as well as other related information about these elements.

1. As an element moves left to right in a period, its atomic size decreases.

This is because within a period, electrons are added to the same valence shell that they’ve been in since before the element’s formation. As these new electrons are added, the nucleus gets a higher effective nuclear charge which attracts the electrons more strongly, pulling them closer to the nucleus and reducing the atomic size.

2. As an element moves to the left, its valence electrons are filled up with more protons, which give the atom a stronger positive charge.

As more and more protons are added to the atom, its effective nuclear charge rises as electron shielding stays unchanged. This causes a greater nuclear attraction between the nucleus and the valence electrons, which tightens up the atom’s valence electron shell and shrinks its atomic radius across the period.

3. As an element moves to the right, its valence electrons are filled with more electrons, which give the atom a higher effective nuclear charge.