Helium has the smallest covalent radius
It is hydrogen.
it's neon
Atomic Radius gets greater down the periodic table and gets smaller to the right in the periodic table. This means, in order of atomic radius, that the five smallest elements are Helium, Neon, Fluorine, Oxygen, and Hydrogen in that order. Check all of it out at http://www.ptable.com/ under properties>radius
Guessing its H+
Francium. The elements of the lower left hand side of the periodic table have the largest atomic radius. The upper right has the smallest.
Helium
It is helium that has the smallest atomic radius. Use the link below to see a list of elements arranged by atomic radius.
Fluorine.
It is krypton as it the far most right on the periodic table, having the smallest radius
Fluorine
It is hydrogen.
Rubidium
francium has the largest ionic radius
Formula unit
Helium usually is listed with the smallest atomic radius when calculated. Hydrogen however has a smaller van der Waals radius The protium isotope of hydrogen has the smallest nucleus radius. It is 1.6 fm
If you are talking about individual atoms, it is hydrogen by mass or helium by radius.
Nitrogen