Chemical bonds — Chemistry, 11–13 years
Atoms join in particular ways, and those joins explain why substances have different properties.
How atoms hold together
A chemical bond is the attraction that holds atoms together in a substance. Some atoms share electrons, while others transfer electrons and then attract oppositely charged particles. The pattern of bonding helps decide whether a substance is a solid, dissolves in water or conducts electricity.
Why bonding matters
Chemists needed an explanation for a puzzle: why can hydrogen and oxygen make water, a substance with properties unlike either gas? The answer is that atoms are rearranged into new groups with new bonds. Thinking about bonds lets us explain properties instead of memorising a separate fact for every substance.
A water molecule
Start with two hydrogen atoms and one oxygen atom. Each hydrogen shares one electron with oxygen, forming two shared pairs; oxygen also keeps two lone pairs. The three atoms are now one H₂O molecule. These bonds make water a stable liquid at ordinary temperatures, unlike hydrogen or oxygen gas.
A reasonable mix-up
It is easy to think that a bond is a tiny stick between atoms, because diagrams draw it that way. In reality, a bond is an attraction involving electrons and electric charges, not a piece of material. The drawing is a useful model, but it does not show the exact shape or motion of the electrons.
Bonds in useful materials
The bonds in a material help engineers choose it for a job. Copper has electrons that move easily, so it is useful in electrical wires; glass has a different bonded structure and does not conduct well. Plastics, medicines and fibres also work because their atoms are joined in particular arrangements.
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