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Is radon a metal, nonmetal or metalloid?

By Radon411 Editorial TeamUpdated How we research

Short answer

Radon is a nonmetal: it is classified as a non-metal and belongs to the noble gases, group 18, with element number 86. It is not a metal or a metalloid, and it is a colorless gas at ordinary temperatures, unlike its neighbors polonium, a metalloid, and radium, a metal.

Next step: a test is the only way to know your home's level. How to test your home

Radon is classified as a non-metal and sits in the noble gas block of the periodic table, alongside helium, neon, argon, krypton and xenon. That is a separate category from the table's metals, such as radium two places along, an alkaline earth metal, and from its metalloids, such as polonium. Its standard state is gas.

At ordinary temperatures radon is a colorless gas. It melts at minus 71 degrees Celsius and boils at minus 61.7 degrees Celsius, and it is essentially inert, taking the last place in the zero group of gases. Metals, by contrast, include the elements radon comes from: refined uranium is a silvery-white metal, and radium is a member of the alkaline-earth group of metals.

So radon belongs with the noble gases, not with the metals or metalloids near it in the table. Its chemistry is limited, but it is radioactive, which is what matters for health.

What to do next: see the radon element guide for the full property table, and test your home, since radon is a gas that can move up from the ground into buildings.

Radon and its neighbors in the periodic table

Radon sits at the end of period 6, and the elements around it span many classes: metals, a metalloid, a halogen and the noble gases. Its own class is clear-cut. It is a non-metal, and within the non-metals it belongs to the noble gases, group 18.

Radon and the elements beside it
Atomic numberElementClassState at room temperature
82Lead (Pb)Post-transition metalSolid
83Bismuth (Bi)Post-transition metalSolid
84Polonium (Po)MetalloidSolid
85Astatine (At)HalogenSolid
86Radon (Rn)Noble gas (non-metal)Gas
87Francium (Fr)Alkali metalSolid
88Radium (Ra)Alkaline earth metalSolid

Why radon is not a metal

Element classes are set by an element's chemical and physical properties and its place in the table. On every count radon falls with the non-metals: it is a colorless gas at ordinary temperatures, it is essentially inert, and it takes the last place in the zero group of gases, the noble gases.

Radon against the metals it comes from
ElementClassWhat it is like
UraniumMetal (actinide)When refined, a silvery-white metal
RadiumAlkaline earth metalBrilliant white when freshly prepared, blackening in air
RadonNon-metal, noble gasA colorless gas at ordinary temperatures

So the answer to "metal, nonmetal or metalloid" is nonmetal. Its neighbor polonium is the metalloid, and radium, two places along, is the metal.

A noble gas: the non-metal family that barely reacts

Radon's electron configuration, [Xe] 6s2 4f14 5d10 6p6, ends in 6s2 6p6, a full outer shell of eight electrons. Its oxidation states are listed as 6, 2 and 0. It is not completely unreactive: fluorine has been reported to react with radon, forming a fluoride, and radon fluoride is its only confirmed compound.

Radon's chemical profile
PropertyRadon
Group18, noble gases
Period6
Electron configuration[Xe] 6s2 4f14 5d10 6p6
Oxidation states6, 2, 0
Electronegativity (Allen scale)2.6
First ionization energy10.745 eV
Confirmed compoundsRadon fluoride only

See is radon a noble gas and why radon and krypton don't bond easily for the chemistry in more depth.

A non-metal that turns into metals

Radon is radioactive, and its decay chain runs from non-metal to metalloid to metal. Radon-222 decays into polonium-218, a metalloid, and the chain ends at lead-206, a post-transition metal. Being radioactive is a separate matter from being a metal: radioactive decay happens in unstable atoms, while an element's class is set by its chemical and physical properties and its place in the table.

Decay chain from uranium-238 through uranium-234, thorium-230 and radium-226 to radon-222, radon's decay products and stable lead-206, with radium-226's half-life of 1600 years and radon-222's of 3.823 days.
Read this figure as text

  1. Uranium-238

    Solid

  2. Uranium-234

    Solid

  3. Thorium-230

    Solid

  4. Radium-226

    Solid

    Half-life 1600 years

  5. Radon-222

    Gas

    Half-life 3.823 days

  6. Radon's decay products

  7. Lead-206

    Solid

  • Uranium-238. More than 99 percent of the uranium found in the environment is in the form of U-238. Uranium decays by alpha particles.
  • Uranium-234. Less than one percent of natural uranium, but much more radioactive.
  • Thorium-230. An intermediate EPA names in the uranium-238 chain.
  • Radium-226. Radium decays to produce radon gas.
  • Radon-222. The most common radon isotope, and an alpha emitter. As a gas it can move up through the ground and into a building.
  • Radon's decay products. Radon gas decays into radioactive particles that can get trapped in your lungs when you breathe.
  • Lead-206. Where the chain ends. Only the final, stable atom in the chain is not radioactive.

EPA names uranium-234, thorium-230, radium-226 and radon-222 as intermediates "such as" these, so the chain has more steps than are drawn. Half-lives are shown only where a cited source states one.

In the uranium-238 decay chain, radon is a gas between solid radium and solid polonium and lead.

That gas, sandwiched between solids, is the reason radon matters for homes: it can travel from the ground into the air, and indoors it builds up. The radon element guide covers the whole chain.

Solid radon is still a non-metal

Cold enough, radon freezes, but it does not become a metal. It melts at 202 K (minus 71 degrees Celsius) and boils at 211.45 K (minus 61.7 degrees Celsius), so it is a liquid only in a narrow band and a gas at any temperature found in a home.

Questions about radon's classification

Is radon a metal, nonmetal or metalloid?

A nonmetal. It is classified as a non-metal and belongs to the noble gases, group 18.

Is radon a solid, liquid or gas?

A gas at room temperature. It melts at minus 71 degrees Celsius and boils at minus 61.7 degrees Celsius.

Is radon a halogen?

No. The halogen next to radon in the table is astatine, element 85. Radon, element 86, is a noble gas.

Is a heavy element always a metal?

No. Radon is element 86, with an atomic mass of about 222, and it is a non-metal. Its heavy neighbors include a metalloid, polonium, and metals such as radium and lead.

What is radon's symbol and atomic number?

Rn, and 86.

Is radon a metalloid?

No. Its neighbor polonium, element 84, is the metalloid. Radon, element 86, is a non-metal in the noble gas group.

What metal does radon come from?

Radium, an alkaline earth metal: radium decays to produce radon gas. Radium in turn comes from uranium, a metal, in the decay chain that begins with uranium-238.

Is radon an inert gas?

Essentially, yes. Radon is described as essentially inert, though fluorine has been reported to react with it, forming a fluoride.

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