Atomic radius of the elements

The radius here is the van der Waals radius: half the distance between the nuclei of two atoms of the element that touch without being bonded. It is in picometres, where 100 pm is one ångström. The values are PubChem’s, published by the US National Institutes of Health. It gives one for 99 of the 118 elements; the rest are hatched in the table below rather than coloured as if they were zero.

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H 120, hydrogen He 140, helium Li 182, lithium Be 153, beryllium B 192, boron C 170, carbon N 155, nitrogen O 152, oxygen F 135, fluorine Ne 154, neon Na 227, sodium Mg 173, magnesium Al 184, aluminium Si 210, silicon P 180, phosphorus S 180, sulfur Cl 175, chlorine Ar 188, argon K 275, potassium Ca 231, calcium Sc 211, scandium Ti 187, titanium V 179, vanadium Cr 189, chromium Mn 197, manganese Fe 194, iron Co 192, cobalt Ni 163, nickel Cu 140, copper Zn 139, zinc Ga 187, gallium Ge 211, germanium As 185, arsenic Se 190, selenium Br 183, bromine Kr 202, krypton Rb 303, rubidium Sr 249, strontium Y 219, yttrium Zr 186, zirconium Nb 207, niobium Mo 209, molybdenum Tc 209, technetium Ru 207, ruthenium Rh 195, rhodium Pd 202, palladium Ag 172, silver Cd 158, cadmium In 193, indium Sn 217, tin Sb 206, antimony Te 206, tellurium I 198, iodine Xe 216, xenon Cs 343, caesium Ba 268, barium La 240, lanthanum Ce 235, cerium Pr 239, praseodymium Nd 229, neodymium Pm 236, promethium Sm 229, samarium Eu 233, europium Gd 237, gadolinium Tb 221, terbium Dy 229, dysprosium Ho 216, holmium Er 235, erbium Tm 227, thulium Yb 242, ytterbium Lu 221, lutetium Hf 212, hafnium Ta 217, tantalum W 210, tungsten Re 217, rhenium Os 216, osmium Ir 202, iridium Pt 209, platinum Au 166, gold Hg 209, mercury Tl 196, thallium Pb 202, lead Bi 207, bismuth Po 197, polonium At 202, astatine Rn 220, radon Fr 348, francium Ra 283, radium Ac 260, actinium Th 237, thorium Pa 243, protactinium U 240, uranium Np 221, neptunium Pu 243, plutonium Am 244, americium Cm 245, curium Bk 244, berkelium Cf 245, californium Es 245, einsteinium Fm no value, fermium Md no value, mendelevium No no value, nobelium Lr no value, lawrencium Rf no value, rutherfordium Db no value, dubnium Sg no value, seaborgium Bh no value, bohrium Hs no value, hassium Mt no value, meitnerium Ds no value, darmstadtium Rg no value, roentgenium Cn no value, copernicium Nh no value, nihonium Fl no value, flerovium Mc no value, moscovium Lv no value, livermorium Ts no value, tennessine Og no value, oganesson

How it changes across a period and down a group

Down a group the radius grows, and this is the trend the van der Waals figures show most cleanly: each period adds a shell of electrons further from the nucleus. Group 1 grows at every step, from hydrogen’s 120 pm to francium’s 348 pm, the largest atom in the table.

Across a period the textbook trend is a contraction, because the nuclear charge rises while the added electrons go into the same shell and are pulled in. These figures follow it only loosely. Period 2 does shrink overall, from lithium’s 182 pm to fluorine’s 135 pm, but boron, at 192 pm, is larger than beryllium before it, and neon is larger than fluorine.

That raggedness belongs to this kind of radius rather than to the trend. A van der Waals radius comes from how closely atoms approach when they are not bonded, measured in crystals and gases, and different compilations give noticeably different figures. The covalent radius many textbook charts plot is taken from bond lengths, and it contracts across a period far more regularly.

Extremes and exceptions

Largest and smallest

• Francium, 348 pm
• Caesium, 343 pm
• Rubidium, 303 pm
• Hydrogen, 120 pm
• Fluorine, 135 pm
• Zinc, 139 pm

The three largest and the three smallest atoms PubChem gives a radius for.

Larger than the element before it in the period

• Hydrogen to helium: 120 to 140 pm
• Beryllium to boron: 153 to 192 pm
• Fluorine to neon: 135 to 154 pm
• Magnesium to aluminium: 173 to 184 pm
• Aluminium to silicon: 184 to 210 pm
• Chlorine to argon: 175 to 188 pm
• Gallium to germanium: 187 to 211 pm
• Arsenic to selenium: 185 to 190 pm
• Bromine to krypton: 183 to 202 pm
• Indium to tin: 193 to 217 pm
• Iodine to xenon: 198 to 216 pm
• Thallium to lead: 196 to 202 pm
• Lead to bismuth: 202 to 207 pm
• Polonium to astatine: 197 to 202 pm
• Astatine to radon: 202 to 220 pm

In the main groups, the places where the radius grows from one element to the next across a period, which a smooth contraction would not allow.

Smaller than the element above it

• Boron to aluminium: 192 to 184 pm
• Titanium to zirconium: 187 to 186 pm
• Silver to gold: 172 to 166 pm
• Tin to lead: 217 to 202 pm
• Tellurium to polonium: 206 to 197 pm

Down a group each period adds a shell, so a smaller atom below a larger one is the exception. Gold, lead and polonium come after the lanthanides, whose fourteen f electrons shield the nucleus poorly, so they are smaller than a group trend predicts. The lanthanides do not explain boron above aluminium and titanium above zirconium, which are best read as the scatter in van der Waals figures described above.

The 99 elements with a value, ranked

Equal values share a rank, marked with =.

No value in PubChem’s table, so not ranked: fermium, mendelevium, nobelium, lawrencium, rutherfordium, dubnium, seaborgium, bohrium, hassium, meitnerium, darmstadtium, roentgenium, copernicium, nihonium, flerovium, moscovium, livermorium, tennessine and oganesson.

The values are facts and free to use; this table’s selection and presentation are © 2026 ScienceQuest.

Caveats

• This is the van der Waals radius, not the covalent or metallic radius. A van der Waals radius is larger than the covalent radius of the same atom, because two bonded atoms overlap and two atoms that merely touch do not, so these values will not match a chart of covalent radii.
• No element from fermium on has a value in PubChem’s table.
• The radius of an atom is not a hard edge. Its electron cloud thins out gradually, so every definition of radius is a convention about where to draw the line, and different ones give different numbers.

See also

• The interactive periodic table, with every element’s details
• Crystal lattice explorer, where atoms pack into solids
• All the elements, each with its own page of data