Element 4 · Alkaline earth metal
Beryllium (Be) — Element 4
Greek beryl mineral
Beryllium (Be) is an alkaline earth metal in Period 2, Group 2 of the periodic table with atomic number 4, standard atomic weight 9.0122 u, and ground-state electron configuration [He] 2s². At standard temperature and pressure it is classified as a solid with 2 valence electrons and common oxidation states +2.
Aerospace alloys, X-ray windows
What are the atomic properties and physical constants of Beryllium?
Reference constants compiled from IUPAC standard atomic weights, the NIST Atomic Spectra Database, and the CRC Handbook.
- Atomic number (Z)
- 4
- Standard atomic mass
- 9.0122 u
- Chemical family
- Alkaline earth metal
- Ground-state configuration
- [He] 2s²
- Electrons per shell
- 2, 2
- Valence electrons
- 2
- Common ion charges / oxidation states
- +2
- Phase at STP
- Solid
- Pauling electronegativity
- 1.57 Pauling
- First ionization energy
- 899 kJ/mol
- Atomic radius
- 112 pm
- Melting point
- 1,287 °C
- Boiling point
- 2,470 °C
- Discovery year
- 1798
- Table coordinate
- Period 2, Group 2
- Radioactivity
- Has stable isotope(s)
How are electrons arranged across Beryllium’s shells?
A neutral Beryllium atom contains 4 electrons distributed across 2 occupied principal energy shells ([He] 2s²). The table below compares Beryllium’s shell occupancy against each shell’s theoretical 2n² capacity.
| Principal Shell (n) | Spectroscopic Letter | Electrons in Be | Max Shell Capacity (2n²) |
|---|---|---|---|
| n = 1 | K | 2 e⁻ | 2 e⁻ |
| n = 2 | L | 2 e⁻ | 8 e⁻ |
Frequently Asked Questions about Beryllium (Be)
What is the atomic mass and atomic number of Beryllium (Be)?
Beryllium (Be) has atomic number Z = 4 (4 protons in its nucleus) and an IUPAC standard atomic weight of 9.0122 u. It sits in Period 2, Group 2 and is classified as an alkaline earth metal.
What is the ground-state electron configuration of Beryllium?
The neutral ground-state electron configuration of Beryllium (Z = 4) is [He] 2s². Across its 2 occupied principal shells (n = 1 to n = 2), the electrons per shell are 2, 2, with 2 valence electrons participating in bonding.
What are the common ion charges and electronegativity of Beryllium?
Beryllium commonly forms +2 oxidation states or ion charges in compounds. Its Pauling electronegativity is 1.57 and its first ionization energy is 899 kJ/mol.
When was Beryllium discovered and what is it used for?
Beryllium was discovered in 1798 (Greek beryl mineral). Aerospace alloys, X-ray windows
How does Beryllium compare to neighboring elements?
Other alkaline earth metal elements: