Boron (B): electron configuration, atomic mass and facts
Boron (B) is element 5 of the periodic table, a metalloid in period 2, group 13. Its electron configuration is [He] 2s2 2p1, with electrons arranged in shells 2, 3, and its standard atomic weight is 10.81 u.
▶ Watch Boron’s electrons orbit in the interactive periodic tableBoron at a glance
| Symbol | B |
|---|---|
| Atomic number | 5 |
| Atomic mass | 10.81 u |
| Category | Metalloid |
| Group | 13 |
| Period | 2 |
| Block | p-block |
| Electron configuration | 1s2 2s2 2p1 |
| Noble-gas shorthand | [He] 2s2 2p1 |
| Electrons per shell | 2, 3 |
| Outer-shell electrons | 3 |
| Electronegativity (Pauling) | 2.04 |
| State at 20 °C | solid |
Where is Boron on the periodic table?
Boron is in period 2, group 13, in the p-block. The period number matches its 2 electron shells, and the block names the subshell its last electrons fill. In the same group, Aluminium sits directly below it. Elements in one group have the same number of outer-shell electrons (3 here), which is why they react in similar ways.
How to work out the electron configuration of Boron
Put 5 electrons into subshells in order of rising energy, filling each before starting the next: 1s² (2), 2s² (4), 2p¹ (5). In shorthand, [He] stands for the 2 electrons of helium, giving [He] 2s² 2p¹.
How electronegative is Boron?
Boron has a Pauling electronegativity of 2.04, ranking 29 of the 100 elements with a known value (fluorine is highest at 3.98). That is in the middle of the range.
Frequently asked questions
What is the electron configuration of Boron?
The electron configuration of Boron (B) is 1s2 2s2 2p1. In noble-gas shorthand it is written [He] 2s2 2p1.
How many electrons does Boron have in each shell?
Boron has 5 electrons arranged in shells as 2, 3. It has 3 electrons in its outer shell.
What is the atomic mass of Boron?
The standard atomic weight of Boron is 10.81 u, so one mole of Boron atoms has a mass of about 10.81 g.
Is Boron a metal?
Boron is a metalloid: its properties sit between those of metals and nonmetals.
Explore nearby elements
More metalloids: Silicon, Germanium, Arsenic, Antimony, Tellurium. See all elements on the periodic table.