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How many valence electrons does radon have?

By Radon411 Editorial TeamUpdated October 1, 2026How we research

Short answer

Radon has 8 valence electrons, the 6s2 and 6p6 electrons in its outermost shell, out of 86 electrons in all. Radon is a noble gas with that full outer shell, and it is essentially inert, though fluorine has been reported to react with it to form radon fluoride.

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

Radon's electron configuration is [Xe] 6s2 4f14 5d10 6p6. The valence electrons are the ones in the outermost shell, here the sixth: 6s2 and 6p6, or 2 + 6 = 8. The 4f14 and 5d10 electrons belong to inner shells and do not count.

Eight is the same valence count as the other heavy noble gases: krypton's configuration ends in 4s2 4p6 and xenon's in 5s2 5p6. All three sit in the noble gas block, and radon and krypton both have an oxidation state of 0. Radon is essentially inert, though fluorine has been reported to react with it to form a fluoride.

In total, a neutral radon atom has 86 electrons, matching its atomic number of 86; the eight valence electrons are the outermost of those. Drawn as a Lewis dot structure, which shows only valence electrons, radon is the symbol Rn with eight dots around it: the filled 6s2 pair and the three filled pairs of 6p6, with no unpaired electron left to share.

What to do next: see the radon element guide for the full property table, and remember that radon's health effects come from its radioactivity, not its chemistry. Test your home to find its level.

Counting radon's valence electrons

Valence electrons are the ones in an atom's outermost shell. Radon's electron configuration is [Xe] 6s2 4f14 5d10 6p6, and its outermost shell is the sixth: 6s2 plus 6p6, or 2 + 6 = 8. Sorting all 86 electrons by shell shows why only those eight count.

Radon's 86 electrons by shell (our count from the configuration)
Shell	Subshells	Electrons
1	1s2	2
2	2s2 2p6	8
3	3s2 3p6 3d10	18
4	4s2 4p6 4d10 4f14	32
5	5s2 5p6 5d10	18
6 (outermost)	6s2 6p6	8

The 4f14 and 5d10 electrons are filled late but belong to inner shells, the fourth and fifth, so they are not valence electrons. The shell counts add up to 86, radon's atomic number.

Eight valence electrons across the noble gases

Radon is in group 18, the noble gases, and every member of the group with a filled s and p outer shell has eight valence electrons. Helium is the exception, with a full first shell of two.

Outer shells of the noble gases
Element	Electron configuration	Outer shell	Valence electrons
Helium	1s2	1s2	2
Neon	[He] 2s2 2p6	2s2 2p6	8
Argon	[Ne] 3s2 3p6	3s2 3p6	8
Krypton	[Ar] 4s2 3d10 4p6	4s2 4p6	8
Xenon	[Kr] 5s2 4d10 5p6	5s2 5p6	8
Radon	[Xe] 6s2 4f14 5d10 6p6	6s2 6p6	8

Radon and its neighbors in period 6

Across period 6, the elements just before radon share its inner configuration and differ only in the 6p subshell. Each step along adds one valence electron until radon fills the shell.

Valence electrons from lead to radon (our count from each configuration)
Element	Outer shell	Valence electrons	Class
Lead (82)	6s2 6p2	4	Post-transition metal
Bismuth (83)	6s2 6p3	5	Post-transition metal
Polonium (84)	6s2 6p4	6	Metalloid
Astatine (85)	6s2 6p5	7	Halogen
Radon (86)	6s2 6p6	8	Noble gas

The Lewis dot structure for radon

A Lewis dot structure shows only valence electrons. For radon it is the symbol Rn with eight dots around it, in four pairs: one pair for 6s2 and three pairs for the filled 6p6. No dot is left unpaired, so there is no single electron to share in a bond. Compare astatine, next door at element 85, with 6s2 6p5: seven dots, one of them unpaired. Helium, with only two valence electrons, is drawn with a single pair.

What a full outer shell means for radon

A full shell leaves radon little reason to react. It is essentially inert and occupies the last place in the zero group of gases. It is not completely unreactive: fluorine has been reported to react with it, and radon fluoride is its only confirmed compound.

Radon's electron-related profile
Property	Radon
Group and period	18 (noble gases), period 6
Classification	Non-metal
Oxidation states	6, 2, 0
First ionization energy	10.745 eV
Confirmed compounds	Radon fluoride only

That chemistry has a practical side. Since radon is a noble gas, it releases from any chemical bonds that attach it and may travel far enough to reach groundwater or the air, and since it is a gas, it is easily inhaled. Indoors, a home traps radon, where it can build up. See why radon and krypton don't bond easily.