Boron (B)
Boron is element 5, a metalloid in group 13, period 2. A neutral atom has 5 protons, 6 neutrons and 5 electrons, 3 of them valence electrons.
Metalloid- Atomic number
- 5
- Atomic mass
- 10.81 u
- Valence electrons
- 3
- Protons · neutrons
- 5 · 6
- Electrons per shell
- 2, 3
- At room temperature
- solid
Bohr model of boron
The Bohr model draws boron as a nucleus of 5 protons and 6 neutrons, with its 5 electrons on 2 circular shells: 2 in shell 1, 3 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 boron
1s² 2s² 2p¹
Short form (noble gas notation): [He] 2s² 2p¹. The [He] stands for the electrons of helium, the noble gas before it.
How many valence electrons does boron have?
Boron has 3 valence electrons.
Boron is in group 13, and for groups 13–18 you subtract 10 from the group number: 13 − 10 = 3. It tends to lose them and form a +3 ion.
Protons, neutrons and electrons
| Protons | 5 | equal to the atomic number |
|---|---|---|
| Electrons | 5 | equal to the protons in a neutral atom |
| Neutrons | 6 | mass number 11 − 5 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.
Boron properties
| Symbol | B |
|---|---|
| Category | Metalloid |
| Group · period · block | 13 · 2 · p |
| Atomic mass | 10.81 u |
| State at 25 °C | solid |
| Melting point | 2,348 K (2,070 °C, 3,770 °F) |
| Boiling point | 4,273 K (4,000 °C, 7,230 °F) |
| Density | 2.37 g/cm³ |
| Electronegativity (Pauling) | 2.04 |
| Atomic radius | 192 pm |
| First ionization energy | 8.298 eV |
| Electron affinity | 0.277 eV |
| Oxidation states | +3 |
| Common ion charge | +3 |
| Discovered | 1808 by Joseph Louis Gay-Lussac |
Where boron sits on the periodic table
Group 13: Aluminum, Gallium, Indium, Thallium, Nihonium.
Questions about boron
How many valence electrons does boron have?
Boron has 3 valence electrons.
How many protons, neutrons and electrons does boron have?
A neutral boron atom has 5 protons and 5 electrons. Its most common form has about 6 neutrons (mass number 11 − 5 protons).
What is the electron configuration of boron?
1s² 2s² 2p¹, written in short form as [He] 2s² 2p¹.
What does the Bohr model of boron look like?
A nucleus of 5 protons and 6 neutrons, circled by 2 electron shells holding 2, 3 electrons.
What is the atomic number of boron?
5. The atomic number is the number of protons in the nucleus, and it is what makes an atom boron.