Model: definition in chemistry
Model: A simplified representation of something too small, large or complex to observe directly, used to explain observations and make predictions. Models can be physical objects, diagrams, equations or ideas.
Chemists rely on models because atoms and molecules cannot be seen in ordinary ways. A model is judged by how well it matches experimental evidence, and it is revised or replaced when new results do not fit. The model of the atom changed several times, from Dalton's solid spheres to Thomson's plum pudding, Rutherford's nuclear atom, Bohr's orbits and today's quantum mechanical model with orbitals. An older model can stay useful when it explains what you need, which is why the Bohr model is still taught.
Examples
- Ball-and-stick kits showing the bent shape of a water molecule
- The Bohr model, with electrons in fixed circular orbits
- The particle model explaining solids, liquids and gases
- The ideal gas law, PV = nRT, a mathematical model of gases
On the periodic table
The periodic table is itself a model that arranges the elements to reveal patterns, and the quantum model of the atom explains why those patterns appear.