Group 2: the alkaline earth metals

Two outer electrons: the ns² pattern

Every group 2 configuration ends in ns², from beryllium ([He] 2s²) to radium ([Rn] 7s²). Losing both s electrons leaves a noble gas arrangement, so the metals form 2+ ions and compounds with simple formulas such as MgO, CaCl₂ and BaSO₄. Removing a second electron costs extra energy, so group 2 metals are less reactive than their group 1 neighbors.

Beryllium is the exception: its tiny atom holds shared electrons so tightly that many of its compounds are covalent, and it often behaves more like aluminum than like magnesium.

Trends down the group, in numbers

Moving down the column, the outer electrons get easier to remove. First ionization energy falls from 9.323 eV for beryllium to 5.212 eV for barium, and electronegativity from 1.57 to 0.89.

Other properties do not follow a neat line. Beryllium melts at 1560 K and magnesium at only 923 K, then calcium rises to 1115 K before the values drift down to 973 K for radium. Density dips to 1.54 g/cm³ at calcium, then climbs to 3.51 g/cm³ for barium and 5.5 g/cm³ for radium.

Where you meet group 2

Your body needs calcium for bones and teeth and magnesium for hundreds of enzymes. Milk of magnesia, Mg(OH)₂, settles upset stomachs, Epsom salt is magnesium sulfate, and drywall is made from gypsum, a calcium sulfate. Strontium salts give fireworks their deep red, and the gem emerald is a variety of beryl, the mineral that gave beryllium its name.

Group 2 and the alkaline earth metals

Here the column and the family are the same six elements, so the alkaline earth metals family page covers their reactions. The group view adds a twist: helium also has an ns² configuration (1s²), yet it sits in group 18, because those two electrons fill its only shell. Radium, discovered by Marie and Pierre Curie in 1898, is radioactive.