Scientific knowledge
Chemical bonding
Atoms can be held together by bonds.
In forming bonds, atoms can achieve a stable electron arrangement. They do this when they have a full outer shell of electrons, either by losing, gaining or sharing electrons.
Covalent bonding
Atoms share electrons to form covalent bonds.
When two atoms make a covalent bond, each atom contributes one electron. The pair of electrons attracts each atom, so the atoms stick together in a molecule.
A Lewis diagram shows the outer shell electrons in a compound.
A double covalent bond is sharing four electrons between two atoms.
Macromolecules are made from networks of atoms covalently bonded together. Graphite and diamond are macromolecules built from carbon atoms, and silicon dioxide forms the macromolecule that makes a quartz crystal.
The formula of a covalent compound is found by making a group of atoms form a molecule where all the atoms have a full outer shell.
Alkanes
Alkenes
Polymers and plastics
Fossil fuels
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