Helium has the smallest covalent radius
It is hydrogen.
Fluorine has the smallest anion radius among the elements.
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
Francium. The elements of the lower left hand side of the periodic table have the largest atomic radius. The upper right has the smallest.
The covalent atomic radius of francium is 260 pm.The covalent atomic radius of caesium is 244 pm.
Helium
It is helium that has the smallest atomic radius. Use the link below to see a list of elements arranged by atomic radius.
It is hydrogen.
Fluorine
The element with the smallest negative ionic radius is fluorine (F). It has a small ionic radius due to the high effective nuclear charge, which attracts the electrons closer to the nucleus in the ionic form.
Fluorine has the smallest anion radius among the elements.
Helium usually is listed with the smallest atomic radius when calculated. Hydrogen however has a smaller van der Waals radius
If you are talking about individual atoms, it is hydrogen by mass or helium by radius.
nitrogen
Formula unit
The period 4 element with the smallest atomic radius is chlorine, which has a greater number of protons in the nucleus pulling the electrons closer, making it smaller compared to other elements in the same period.
Fluorine has the smallest atomic radius among fluorine, chlorine, bromine, iodine, and astatine.