Difference between ionic radius and atomic radius
Ionic radius and atomic radius both describe the size of an atom, but they differ based on the context in which they are used.
Atomic radius refers to the size of a neutral atom. It is typically defined as the distance from the nucleus to the outermost electron shell or the outermost electron cloud. The atomic radius generally increases as you move down a group (column) in the periodic table, and decreases as you move across a period (row) from left to right. This trend is due to the increasing number of energy levels (shells) in the atom as you move down a group, and the increasing nuclear charge (protons) attracting the outermost electrons, causing the atomic radius to decrease from left to right.
Ionic radius, on the other hand, refers to the size of an ion, which is an atom that has gained or lost electrons to become positively or negatively charged. When an atom loses electrons to form a cation (positively charged ion), its radius generally decreases compared to the original atomic radius. This is because the removal of electrons reduces the repulsive forces within the electron cloud, causing the remaining electrons to be pulled closer to the nucleus. Conversely, when an atom gains electrons to form an anion (negatively charged ion), its radius generally increases compared to the original atomic radius. The additional electrons introduce more repulsive forces, causing the electron cloud to spread out and increase in size.
To determine the atomic radius or ionic radius of a specific atom, you can refer to a periodic table or consult reliable sources that provide atomic and ionic radii data. These radii values are experimentally determined using various techniques, such as X-ray crystallography or electron diffraction.