Covalent Atomic Radius of elements
Introduction:
Atoms are often depicted as spheres, with a central nucleus composed of protons and neutrons. Surrounding this nucleus is a cloud-like region containing negatively charged electrons. An atom’s radius is typically measured from its center to the outermost electron shell. However, the exact shape and size of this electron cloud can vary significantly based on the atom’s bonding interactions with neighboring atoms.
The covalent atomic radii presented in the graph below are based on crystallographic data for most of the elements. Reference: Cordero et al. Covalent radii revisited. Dalton Trans. 7:2832-8, 2008. https://doi.org/10.1039/b801115j
The radii are given in angstrom (Å) unit that is equal to 10−10 meter, or 0.1 nanometer (nm).
Most of the atomic radii graphs available on the internet show van der Waals radii. The covalent radii shown here are at least 0.5 Å shorter than the van der Waals radii.
Additional comments
There is no single element that forms a significant number of structurally characterized bonds to all elements of the periodic table. Therefore the authors defined covalent radii from experimental bond distances mainly to N, C or O based on analysis of more than 228,000 experimental bond distances.
Trends in the data
In each period, Group 1 elements (H, Li, Na, K, Rb, Cs, Fr - alkaline metals) have the largest radii. Within each period, there is a sharp decrease of the covalent radii from Group 1 to Group 13 elements. The changes from Group 13 to Group 18 are much less pronounced.