Boron (B)
Element 5 · metalloid · group 13, period 2
Boron is element 5, a metalloid in group 13 and period 2. Its electron configuration is [He] 2s2 2p1. That leaves 3 valence electrons in the outer shell, with the shells filling 2, 3. Losing its 3 valence electrons is the shorter route to a full shell, so it carries a charge of +3.
- 5 protons
- 3 valence e−
- +3
- p-block
Properties
| Atomic number | 5 |
|---|---|
| Symbol | B |
| Standard atomic weight | 10.81 u |
| Group | 13 |
| Period | 2 |
| Block | p-block |
| Category | metalloid |
| Electron configuration | 1s2 2s2 2p1 |
| Noble-gas notation | [He] 2s2 2p1 |
| Electrons per shell | 2, 3 |
| Valence electrons | 3 |
| Common ionic charge | +3 |
| Electronegativity (Pauling) | 2.04 |
| Protons / electrons | 5 / 5 |
Electron configuration of boron
Orbitals fill from the lowest energy upward. Writing that out for boron gives 1s2 2s2 2p1, which is 1s2 2s2 2p1 in plain text.
Everything up to He is the same as in that noble gas, so it is usually abbreviated to [He] 2s2 2p1. The part outside the bracket is what does the chemistry.
| Subshell | Electrons | Capacity |
|---|---|---|
| 1s | 2 | 2 |
| 2s | 2 | 2 |
| 2p | 1 | 6 |
Boron ion charge
Boron commonly forms ions with a charge of +3.
It has 3 valence electrons, so it is 5 short of a full octet and 3 above an empty outer shell. An atom takes whichever route is shorter, which is why the charge comes out as it does.
Common questions
How many valence electrons does boron have?
Boron has 3 valence electrons. For a main-group element the count is the group number minus 10, and boron is in group 13.
What is the electron configuration of boron?
1s2 2s2 2p1, or [He] 2s2 2p1 written from the previous noble gas. Orbitals fill lowest energy first.
What is the charge of boron?
Boron commonly forms ions with a charge of +3. With 3 valence electrons it is 5 short of an octet and 3 above an empty shell, so it takes whichever route is shorter.
How many protons, electrons and neutrons does boron have?
A neutral boron atom has 5 protons and 5 electrons. Its standard atomic weight is 10.81, so the most common isotope has about 6 neutrons.
Nearby elements
See the ionic charge of every element →