All practice pages/Interatomic theory/Elements
Element 5, a metalloid
A hard black metalloid that plants need, heat-proof glass depends on, and the strongest permanent magnets contain.
Period 2, group 13. The other metalloids are tinted, and every cell opens its own article.
Boron has 5 electrons, one for every proton, so the atom carries no charge. Below are the same 5 electrons written two ways.
1s² 2s² 2p¹
Short form: [He] 2s² 2p¹, where [He] stands for the 2 electrons helium already has.
The simple form counts electrons shell by shell. The orbital form says which subshell each one sits in: s holds 2, p holds 6, d holds 10 and f holds 14. Shell 2 here is 2s² 2p¹, and 2 + 1 is 3.
Boron sits in period 2 and has 2 shells. The period number counts the shells.
The outer shell holds 3 electrons. Those are the ones boron can lose, gain or share, so they are the ones that decide what it bonds with. For a main-group element the group number gives that count: group 13 means 3.
Three valence electrons. Boron is too small and holds its electrons too tightly to form B³⁺ ions, so it shares electrons in covalent bonds, often ending up with only six electrons around it instead of eight.
Never free in nature. It is mined as borate minerals such as borax and kernite, mostly in Turkey and in the Mojave Desert town of Boron, California. Plants need a trace of it to grow.
Joseph Louis Gay-Lussac and Louis Jacques Thénard, and separately Humphry Davy, isolated impure boron in 1808. The name joins borax, from the Arabic buraq, with the ending of carbon, which boron resembles.
Borosilicate glass, the heat-resistant kind in lab glassware and oven dishes, uses a large share. Borax goes into detergents and homemade slime, and boric acid is a mild antiseptic and insecticide. Boron carbide is among the hardest materials made and goes into body armor. Boron-10 absorbs neutrons, so it helps control nuclear reactors, and boron is part of the neodymium magnets in motors and headphones.