Beryllium (Be)
Beryllium is element 4, an alkaline earth metal in group 2, period 2. A neutral atom has 4 protons, 5 neutrons and 4 electrons, 2 of them valence electrons.
Alkaline earth metal- Atomic number
- 4
- Atomic mass
- 9.012 u
- Valence electrons
- 2
- Protons · neutrons
- 4 · 5
- Electrons per shell
- 2, 2
- At room temperature
- solid
Bohr model of beryllium
The Bohr model draws beryllium as a nucleus of 4 protons and 5 neutrons, with its 4 electrons on 2 circular shells: 2 in shell 1, 2 in shell 2. Press Build the atom to watch the shells fill from the inside out. The outer ring (the L shell) is dashed: the electrons there are the ones that take part in chemistry.
Real electrons don't travel in neat circles. They live in fuzzy orbitals, shown below, but the Bohr picture is the quickest way to count shells and valence electrons.
Electron configuration of beryllium
1s² 2s²
Short form (noble gas notation): [He] 2s². The [He] stands for the electrons of helium, the noble gas before it.
How many valence electrons does beryllium have?
Beryllium has 2 valence electrons.
Beryllium is in group 2, so it has 2 valence electrons. It tends to lose them and form a +2 ion.
Protons, neutrons and electrons
| Protons | 4 | equal to the atomic number |
|---|---|---|
| Electrons | 4 | equal to the protons in a neutral atom |
| Neutrons | 5 | mass number 9 − 4 protons |
Atoms of the same element can have different numbers of neutrons (isotopes). The count above uses the rounded atomic mass, the way it's taught in class.
Beryllium properties
| Symbol | Be |
|---|---|
| Category | Alkaline earth metal |
| Group · period · block | 2 · 2 · s |
| Atomic mass | 9.012 u |
| State at 25 °C | solid |
| Melting point | 1,560 K (1,290 °C, 2,350 °F) |
| Boiling point | 2,744 K (2,470 °C, 4,480 °F) |
| Density | 1.85 g/cm³ |
| Electronegativity (Pauling) | 1.57 |
| Atomic radius | 153 pm |
| First ionization energy | 9.323 eV |
| Electron affinity | — |
| Oxidation states | +2 |
| Common ion charge | +2 |
| Discovered | 1798 by Louis Nicolas Vauquelin |
Where beryllium sits on the periodic table
Group 2: Magnesium, Calcium, Strontium, Barium, Radium.
Questions about beryllium
How many valence electrons does beryllium have?
Beryllium has 2 valence electrons.
How many protons, neutrons and electrons does beryllium have?
A neutral beryllium atom has 4 protons and 4 electrons. Its most common form has about 5 neutrons (mass number 9 − 4 protons).
What is the electron configuration of beryllium?
1s² 2s², written in short form as [He] 2s².
What does the Bohr model of beryllium look like?
A nucleus of 4 protons and 5 neutrons, circled by 2 electron shells holding 2, 2 electrons.
What is the atomic number of beryllium?
4. The atomic number is the number of protons in the nucleus, and it is what makes an atom beryllium.