- 88 total number
- Not Applicable ()
The alkaline earth metals occupy group two of the periodic table. In order of increasing atomic number they are beryllium, magnesium, calcium, strontium, barium and radium. They all occur naturally and are all shiny silvery-white in appearance as well as being fairly reactive under room temperatures and pressures. Radium, the heaviest – with an atomic number of 88 – was discovered by Marie and Pierre Curie in 1898 and is the only radioactive member of these metals.
Radium used to be used in luminous paints for aircraft dials, watches and switches. This practice continued until the 1960s when the harmfulness to humans was better understood.