CHEMISTRY GLOSSARY

atomic clock    →   atomski sat

Atomic clock is an apparatus for standardizing time based on periodic phenomena within atoms or molecules (ammonia clock; caesium clock).

atomic number    →   atomski broj

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 absorption spectroscopy    →   atomska apsorpcijska spektroskopija

Atomic absorption spectroscopy (AAS) An analytical technique in which a sample is vapourised and the nonexcited atoms absorb electromagnetic radiation at characteristic wavelengths.

atomic orbital    →   atomska orbitala

Atomic orbital is a wave function that describes the behaviour of an electron in an atom.

atomic spectroscopy    →   atomska spektroskopija

Atomic spectroscopy is an expensive analytical method which uses absorption (AAS), emission (AES) and fluorescent (AFS) characteristics of the analyte.

atomic weight    →   atomska težina

See Relative atomic mass.

Dalton’s atomic theory    →   Daltonova atomska teorija

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).

relative atomic mass    →   relativna atomska masa

Relative atomic mass (A_r) is the ratio of the average mass per atom of the naturally occurring form of an element to 1/12 of the mass of nuclide ¹²C. The term atomic weight is synonymous with the relative atomic mass.

unified atomic mass unit    →   unificirana atomska jedinica mase

Unified atomic mass unit (u or m_u) is a unit of mass used in atomic, molecular, and nuclear science, defined as the mass of one atom of ¹²C divided by 12. Its approximate value is

AAS    →   AAS

AAS is abbreviation for atomic absorption spectroscopy.