How many protons and electrons does radon have?

The number of protons in the nucleus is what makes an atom a particular element. Isotopes are forms of the same element with the same number of protons but a different number of neutrons, so every radon atom, whatever its isotope, has 86 protons. Change the proton count and the atom becomes a different element, which is exactly what happens in radioactive decay.

Each alpha decay removes two protons and two neutrons, because that is what an alpha particle is. So radium-226 (88 protons) becomes radon-222 (86), and radon-222 becomes polonium-218 (84). Radon is the only gas in the chain, and as a noble gas it releases from any chemical bonds that attach it and can travel far enough to reach the air.

Radon's electron configuration is [Xe] 6s2 4f14 5d10 6p6. The [Xe] is shorthand for xenon's 54 electrons, the configuration of the noble gas before it, and the rest adds 32 more.

The last two groups, 6s2 and 6p6, form the outer shell: eight electrons, a full set, the mark of a noble gas. Radon is essentially inert. The valence electrons page draws its Lewis dot structure.

A radon atom on its own is neutral: 86 protons and 86 electrons. Chemistry changes that only rarely. Radon's oxidation states are listed as 6, 2 and 0, fluorine has been reported to react with it to form a fluoride, and radon fluoride is its only confirmed compound.

With 86 protons, every radon nucleus is unstable. Thirty-nine radon isotopes are known, from radon-193 to radon-231, and each one has a half-life and a decay mode; there is no stable radon. Their neutron counts run from 107 to 145 (calculated: mass number minus 86).

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1. 238U

   Uranium-238

   Solid

2. 234U

   Uranium-234

   Solid

3. 230Th

   Thorium-230

   Solid

4. 226Ra

   Radium-226

   Solid

   Half-life 1600 years

5. 222Rn

   Radon-222

   Gas

   Half-life 3.823 days

6. ···

   Radon's decay products

7. 206Pb

   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.

Radon-222, the most common isotope, has 136 neutrons and a half-life of about 3.8 days, and it is an alpha emitter. Those alpha particles, two protons and two neutrons each, are why radon matters for health: inhaled, they can damage sensitive tissue. See is radon radioactive and how many neutrons radon has.