Alkaline Earth Metals (Group 2)
Beryllium, magnesium, calcium, strontium, barium and radium: group 2 metals with two outer electrons and a steady 2+ charge.
What they have in common
Group 2 elements end in ns². Giving up both electrons produces a 2+ ion with a noble-gas configuration. They are reactive, but less so than their group 1 neighbours, because a doubly charged ion requires more energy to form.
The name comes from their oxides (“earths”), which are basic (alkaline) in water. Calcium and magnesium are the everyday ones: bones, limestone, chlorophyll and hard water all come down to these two.
- Two valence electrons (ns²)
- Form 2+ ions
- Harder and denser than the alkali metals
- Reactivity increases down the group
- Several give characteristic flame colours (Ca orange-red, Sr crimson, Ba green)
Alkaline earth metals at a glance
| Element | Z | Mass | Configuration | Valence e⁻ | Charges | EN | Radius (pm) |
|---|---|---|---|---|---|---|---|
| Beryllium (Be) | 4 | 9.012 | [He] 2s2 | 2 | 2+ | 1.57 | 90 |
| Magnesium (Mg) | 12 | 24.305 | [Ne] 3s2 | 2 | 2+ | 1.31 | 130 |
| Calcium (Ca) | 20 | 40.078 | [Ar] 4s2 | 2 | 2+ | 1 | 174 |
| Strontium (Sr) | 38 | 87.62 | [Kr] 5s2 | 2 | 2+ | 0.95 | 192 |
| Barium (Ba) | 56 | 137.327 | [Xe] 6s2 | 2 | 2+ | 0.89 | 198 |
| Radium (Ra) | 88 | [226] | [Rn] 7s2 | 2 | 2+ | 0.9 | — |
Questions students ask
Why are they called alkaline earth metals?
Their oxides were once called “earths”, and they dissolve to form alkaline (basic) solutions.
What charge do alkaline earth metals have?
2+. They lose both ns² electrons.