The atomic radius is the distance from the center of an atom's nucleus to the outermost electrons. It is a measure of the size of an atom.
Atomic radius is typically measured in picometers (pm) or angstroms (Å) using various experimental techniques such as X-ray crystallography or spectroscopy.
Atomic radius generally decreases from left to right across a period in the periodic table due to the increasing number of protons and electrons, which leads to a stronger pull on the outermost electrons. However, atomic radius increases from top to bottom within a group due to the addition of new energy levels.
Atomic radius refers to the size of an atom in its neutral state, while ionic radius refers to the size of an ion (an atom with a positive or negative charge) due to the loss or gain of electrons. Ionic radius is typically larger than atomic radius due to the change in electron configuration.
Isotopes, which are atoms of the same element with different numbers of neutrons, have the same atomic radius as they have the same number of protons and electrons. However, isotopes with more neutrons may have a slightly larger atomic radius due to the increased mass of the nucleus.