Chemical bonding — Chemistry, 14–17 years
Atoms join because their electrons can settle into more stable arrangements. Ionic and covalent bonding explain why substances have different structures and properties.
How atoms hold together
Atoms can join when their outer electrons are transferred or shared. In ionic bonding, one atom gives electrons to another and oppositely charged ions attract; in covalent bonding, atoms share electrons, forming molecules such as H₂O.
Why bonding matters
Chemists needed to explain why sodium chloride is a crystal, water is a liquid and oxygen is a gas, even though all are made of atoms. Bonding links an invisible electron arrangement to visible properties such as melting point, hardness and electrical conductivity.
Making sodium chloride
A sodium atom has one outer electron and chlorine needs one more for a stable outer shell. Sodium transfers that electron, becoming Na⁺; chlorine receives it, becoming Cl⁻. Their opposite charges attract, so the formula is NaCl, with a 1:1 ratio of ions.
Atoms do not become magnets
It is easy to picture ionic bonding as atoms sticking together like tiny magnets. The picture is useful for attraction, but it hides the electron transfer and the repeating crystal lattice; NaCl is not made of separate NaCl molecules floating around in the solid.
Choosing useful materials
Battery designers use ion movement in ionic materials, while plastics, medicines and fuels depend on covalent molecules with particular shapes. Knowing the bonding does not predict every detail, but it helps scientists choose or design materials with suitable strength, solubility or conductivity.
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