Dalton’s atomic theory is a theory of chemical combination, first stated by John Dalton in 1803. It involves the following postulates:
1. Elements consist of indivisible small particles (atoms).
2. All atoms of the same element are identical; different elements have different types of atom.
3. Atoms can neither be created nor destroyed.
4. ’Compound elements’ (i.e. compounds) are formed when atoms of different elements join in simple ratios to form ’compound atoms’ (i.e. molecules).
Dalton also proposed symbols for atoms of different elements (later replaced by the present notation using letters).
Dalton, John (1766-1844) British chemist and physicist. In 1801 he formulated his law of partial pressures (Dalton’s law), but he is best remembered for Dalton’s atomic theory, which he announced in 1803. Dalton also studied colour blindness (a condition, once called Daltonism, that he shared with his brother).
Ligand field theory is a description of the structure of crystals containing a transition metal ion surrounded by nonmetallic ions (ligands). It is based on the construction of molecular orbitals involving the d-orbitals of the central metal ion and combinations of atomic orbitals of the ligands.
Valence bond theory is a theory that explains the shapes of molecules in terms of overlaps between half-filled atomic orbitals, or half filled hybridised orbitals.
Atomic absorption spectroscopy (AAS) An analytical technique in which a sample is vapourised and the nonexcited atoms absorb electromagnetic radiation at characteristic wavelengths.
Atomic clock is an apparatus for standardizing time based on periodic phenomena within atoms or molecules (ammonia clock; caesium clock).
Atomic number (Z) is a characteristic property of an element, equal to the number of protons in the nucleus. The atomic number and the element symbol are two alternate ways to label an element. In nuclide symbols, the atomic number is a leading subscript; for example, in 2He.
Atomic orbital is a wave function that describes the behaviour of an electron in an atom.
Atomic spectroscopy is an expensive analytical method which uses absorption (AAS), emission (AES) and fluorescent (AFS) characteristics of the analyte.
Generalic, Eni. "Dalton%E2%80%99s atomic theory." Croatian-English Chemistry Dictionary & Glossary. 29 June 2022. KTF-Split. {Date of access}. <https://glossary.periodni.com>.
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