Beryllium (Be): electron configuration, atomic mass and facts
Beryllium (Be) is element 4 of the periodic table, an alkaline earth metal in period 2, group 2. Its electron configuration is [He] 2s2, with electrons arranged in shells 2, 2, and its standard atomic weight is 9.0122 u.
▶ Watch Beryllium’s electrons orbit in the interactive periodic tableBeryllium at a glance
| Symbol | Be |
|---|---|
| Atomic number | 4 |
| Atomic mass | 9.0122 u |
| Category | Alkaline earth metal |
| Group | 2 |
| Period | 2 |
| Block | s-block |
| Electron configuration | 1s2 2s2 |
| Noble-gas shorthand | [He] 2s2 |
| Electrons per shell | 2, 2 |
| Outer-shell electrons | 2 |
| Electronegativity (Pauling) | 1.57 |
| State at 20 °C | solid |
Where is Beryllium on the periodic table?
Beryllium is in period 2, group 2, in the s-block. The period number matches its 2 electron shells, and the block names the subshell its last electrons fill. In the same group, Magnesium sits directly below it. Elements in one group have the same number of outer-shell electrons (2 here), which is why they react in similar ways.
How to work out the electron configuration of Beryllium
Put 4 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4). In shorthand, [He] stands for the 2 electrons of helium, giving [He] 2s².
How electronegative is Beryllium?
Beryllium has a Pauling electronegativity of 1.57, ranking 52 of the 100 elements with a known value (fluorine is highest at 3.98). That is in the middle of the range.
Frequently asked questions
What is the electron configuration of Beryllium?
The electron configuration of Beryllium (Be) is 1s2 2s2. In noble-gas shorthand it is written [He] 2s2.
How many electrons does Beryllium have in each shell?
Beryllium has 4 electrons arranged in shells as 2, 2. It has 2 electrons in its outer shell.
What is the atomic mass of Beryllium?
The standard atomic weight of Beryllium is 9.0122 u, so one mole of Beryllium atoms has a mass of about 9.0122 g.
Is Beryllium a metal?
Yes. Beryllium is an alkaline earth metal.
Explore nearby elements
More alkaline earth metals: Magnesium, Calcium, Strontium, Barium, Radium. See all elements on the periodic table.