Covalent radius

Definition

Covalent radius is the measure of the size of an atom that forms part of a single covalent bond. It represents half the distance between two identical atoms bonded together in a molecule.

5 Must Know Facts For Your Next Test

1. Covalent radius generally decreases across a period from left to right due to increasing effective nuclear charge.
2. Covalent radius increases down a group as additional electron shells are added, increasing the atomic size.
3. The measurement of covalent radii can help predict molecular geometries and bond lengths in molecules.
4. Elements with smaller covalent radii typically have stronger bond energies because their atoms are closer together.
5. Transition metals can have multiple covalent radii depending on their oxidation states and coordination numbers.

Review Questions

• What trend does covalent radius follow across a period?
• How does the addition of electron shells affect the covalent radius down a group?
• Why is knowledge of covalent radii important for predicting molecular geometries?

Related terms

Atomic Radius: A measure of the size of an atom, usually the mean or typical distance from the nucleus to the boundary of the surrounding cloud of electrons.

Ionic Radius: The measure of an atom's ion in a crystal lattice. It varies based on whether an ion is gaining or losing electrons.

Van der Waals Radius: A measure of how close atoms can approach each other without forming a bond, representing half the distance between two non-bonded atoms at their closest approach.