Group 2 elements of the periodic table
Alkaline earth metals are six chemical elements in group 2 of the periodic table: beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). They have two valence electrons and form ions with a +2 charge.
Read in glossary99% of calcium in the human body is found in bones and teeth
Magnesium burns with a brilliant white flame and is used in signal flares
Radium was discovered by Marie Curie and is a radioactive element
Beryllium is used in aviation due to its lightness and strength
Strontium gives fireworks their bright red color
All alkaline earth metals have an outer electron configuration of ns², where n is the period number. This accounts for their typical +2 oxidation state.
Alkaline earth metals are less reactive than alkali metals but still quite active. Reactivity increases down the group. Beryllium is least reactive, while barium reacts even with cold water.
Reaction with water depends on the element. Beryllium barely reacts, magnesium reacts slowly with hot water, calcium slowly with cold water, and barium reacts vigorously.
M + 2H₂O → M(OH)₂ + H₂↑| Element | Z | Mass u | M.P. °C | B.P. °C | ρ г/см³ | EN |
|---|---|---|---|---|---|---|
Be Beryllium | 4 | 9.01 ▼ | 1287 ▲ | 2469 ▲ | 1.85 | 1.57 ▲ |
Mg Magnesium | 12 | 24.30 | 650 ▼ | 1090 ▼ | 1.74 | 1.31 |
Ca Calcium | 20 | 40.08 | 842 | 1484 | 1.55 ▼ | 1.00 |
Sr Strontium | 38 | 87.62 | 777 | 1382 | 2.64 | 0.95 |
Ba Barium | 56 | 137.33 | 727 | 1897 | 3.62 | 0.89 ▼ |
Ra Radium | 88 | 226.03 ▲ | 700 | 1140 | 5.00 ▲ | 0.90 |
The name 'alkaline earth' comes from the fact that the oxides of these metals ('earths' in old chemical terminology) have alkaline properties. Originally the term applied only to oxides, but later extended to the elements themselves.
Joseph Black proved that magnesia (MgO) differs from lime (CaO)
Humphry Davy discovered calcium, barium, and strontium by electrolysis
Friedrich Wöhler and Antoine Bussy independently isolated beryllium
Marie and Pierre Curie discovered radium while studying uranium ore
Discovered calcium, barium, and strontium by electrolysis
Discovered radium and polonium, two-time Nobel Prize laureate
First to isolate beryllium and aluminum in pure form