All practice pages/Interatomic theory/Elements
Element 86, a noble gas
A radioactive noble gas that seeps out of the ground into basements, and a leading cause of lung cancer.
Period 6, group 18. The other noble gases are tinted, and every cell opens its own article.
Radon has 86 electrons, one for every proton, so the atom carries no charge. Below are the same 86 electrons written two ways.
1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 4f¹⁴ 5s² 5p⁶ 5d¹⁰ 6s² 6p⁶
Short form: [Xe] 4f¹⁴ 5d¹⁰ 6s² 6p⁶, where [Xe] stands for the 54 electrons xenon already has.
That list runs by shell. In the order the subshells fill it reads [Xe] 6s² 4f¹⁴ 5d¹⁰ 6p⁶, because a subshell fills by its energy, not by its shell number.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 4 here is 4s² 4p⁶ 4d¹⁰ 4f¹⁴, and 2 + 6 + 10 + 14 is 32.
Radon sits in period 6 and has 6 shells. The period number counts the shells.
The outer shell holds 8 electrons. Those are the ones radon can lose, gain or share, so they are the ones that decide what it bonds with. For a main-group element the group number gives that count: group 18 means 8.
A full valence shell, like the other noble gases, but its outer electrons are held loosely enough that it can form a fluoride. Its radioactivity makes that chemistry hard to study.
Made continuously in soil and rock as uranium and radium decay. It seeps into buildings, especially basements, and is the largest source of natural radiation for most people.
Ernest Rutherford and Robert Owens noticed a radioactive gas given off by thorium in 1899, and Friedrich Ernst Dorn found the one given off by radium in 1900. William Ramsay and Robert Whytlaw-Gray isolated it in 1908 and called it niton, from the Latin for shining. The name radon, after radium, was adopted in 1923.
Once used in cancer radiotherapy; today it is measured far more than it is used. Radon levels help scientists trace the movement of air and groundwater and study earthquakes.
Breathing radon for years raises the risk of lung cancer, especially for smokers; in the United States it is the second leading cause of lung cancer after smoking. Home test kits are cheap, and ventilating basements lowers the level.