What is the atom Radius?

Let’s talk about the an interpretation of the atom radius, also called atomic size, and also the atomic radius trend on the regular table. The atom radius is measure up as half the distance between two nuclei the the exact same atoms that room bonded together. While your initial assumed may have been to measure up the street from the center of an atom’s nucleus come the leaf of its electron cloud, this is inaccurate and also not feasible. This is since the boundaries of orbitals are fairly fuzzy, and also they also adjust under different conditions. For this reason the atomic radius is measured as displayed in the diagram below.

You are watching: Which element has the smallest atomic radius?


Atomic Radius tendency on the periodic Table


Atomic radii rise toward the bottom left corner of the periodic table, with Francium having actually the largest atomic radius. Atom decrease in size throughout the period and rise in dimension down the group. Let’s malfunction the trend into its period and group trends.

Period Trends

There are countless trends ~ above the periodic table. Because that example, ionization energy, electronegativity, and also of course atomic radius which we will talk about now. Throughout a period, atomic radii decrease. This is because while the variety of electrons rises down the period, castle only add to the very same main energy level, and also therefore execute not expand the electron cloud. Down the period, however, the variety of protons likewise increases. This raised positive fee attracts or pulls, the electrons in closer come the nucleus, diminish the atomic radius.


One thing to note is that the impact of the attraction in between the positively charged nucleus and the electrons is slightly countered by the repulsion the electrons as they are successively added. This is why the distinction in atomic radii decreases under each period.

Group Trend

Down a group, atom radii increase. This is due to the fact that between each group, electrons occupy successively greater energy levels. As electron cloud size increase, so do atomic radii.


The tendency on a Graph

As displayed in the graph below, the atom radius is largest at the first element in every period, and it decreases down each period.

See more: What To Put In Gas Tank To Ruin Engine ? (The Best Ways) Bleach In A Gas Tank


Smallest and also Largest atom Radius

Francium has the largest atomic dimension on the routine table, and also helium has actually the the smallest atomic size.