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
Boron Lewis dot structure
Boron has 3 valence electrons, so its Lewis symbol carries 3 dots: three single dots. The dots go one to a side before any of them pair up, so the unpaired ones show exactly how many bonds the atom tends to form. The ion has given those electrons away, which is why it is drawn in brackets with none.
Draw it in the Lewis structure generator →
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
What is the Lewis dot structure of boron?
The symbol B with 3 dots, one for each valence electron: three single dots. Dots go one to a side before any pair up, the same way electrons fill separate orbitals before sharing one. The B3+ ion is drawn in brackets with no dots, because it has lost them.
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.
Boron in Lewis structures
What the configuration above means in practice. Boron brings 3 valence electrons to each of these, and the working on every one of them starts by counting exactly that.
Nearby elements
See the ionic charge of every element →