49.012BeBeryllium
Beryllium (Be) — element 4alkaline earth metal · group 2, period 2
Beryllium is a chemical element with the symbol Be and atomic number 4. It is an alkaline earth metal in group 2, period 2 of the periodic table (the s-block), with a standard atomic mass of 9.012 u. At room temperature (25 °C) beryllium is a solid.
💡 Known for: A light, very stiff metal used in aerospace parts, X-ray windows and the mirrors of the James Webb Space Telescope.
# Beryllium properties
| Symbol | Be |
|---|---|
| Atomic number | 4 |
| Atomic mass | 9.012 u |
| Category | alkaline earth metal |
| Group | 2 |
| Period | 2 |
| Block | s-block |
| Electron configuration | [He] 2s² |
| Full configuration | 1s² 2s² |
| Electrons per shell | 2, 2 |
| Protons / electrons | 4 / 4 |
| State at 25 °C | solid |
| Melting point | 1560 K (1286.8 °C, 2348.3 °F) |
| Boiling point | 2744 K (2470.8 °C, 4479.5 °F) |
| Density | 1.85 g/cm³ |
| Electronegativity (Pauling) | 1.57 |
| First ionization energy | 9.323 eV |
| Atomic radius | 112 pm |
| Discovered | 1798 |
# Electron configuration of beryllium
The electron configuration of beryllium is [He] 2s², written out in full as 1s² 2s². Its 4 electrons fill 2 shells as 2, 2, so the outermost shell holds 2 electrons. As a group 2 element, beryllium has 2 valence electrons.
# Related elements
LiLithiumprevious elementBBoronnext elementMgMagnesiumgroup 2CaCalciumgroup 2SrStrontiumgroup 2BaBariumgroup 2RaRadiumgroup 2
# Beryllium FAQ
What is the atomic number of beryllium?
The atomic number of beryllium is 4: every beryllium atom has 4 protons in its nucleus. Its symbol is Be.
What is the atomic mass of beryllium?
The standard atomic mass of beryllium is 9.012 u.
What is the electron configuration of beryllium?
Beryllium's electron configuration is [He] 2s² (1s² 2s²), with 2, 2 electrons per shell.
Is beryllium a metal?
Yes. Beryllium is an alkaline earth metal, one of the metals.
What is the melting point of beryllium?
Beryllium melts at 1560 K (1286.8 °C, 2348.3 °F) and boils at 2744 K (2470.8 °C, 4479.5 °F).
What is beryllium used for / known for?
A light, very stiff metal used in aerospace parts, X-ray windows and the mirrors of the James Webb Space Telescope.