atom /atˈəm/

1. The smallest particle in an element which can take part in a chemical reaction, consisting of a nucleus and one or more orbiting electrons (chem)
2. A hypothetical particle of matter so small as to be incapable of further division, according to atomic philosophy (see below)
3. Anything very small

atomic /ə-tomˈik/ adjective

1. Relating to atoms
2. Obtained by means of atomic fission, as atomic energy or atomic power
3. Driven by atomic power, as atomic aircraft-carrier, submarine, etc
4. Heated by atomic power, as atomic radiator

atomˈical adjective

atomˈically adverb

atomicity /at-əm-isˈi-ti/ noun (chem)

1. The state or fact of being composed of atoms
2. The number of atoms in a molecule
3. Valency

atˈomism noun

1. The doctrine that atoms arranged themselves into the universe
2. Atomic philosophy
3. The atomic theory
4. A theory that mental processes and psychological states can be analysed into simple elements (psychology)

atˈomist noun

A person who believes in atomism

atomisˈtic adjective

atomistˈically adverb

atomizāˈtion or atomisāˈtion noun

1. The reduction of liquids to the form of spray
2. Reduction into small units, splintering, fragmentation

atˈomize or atˈomise transitive verb

1. To reduce to atoms
2. To reduce (a liquid or solid) to a fine spray or minute particles
3. To destroy by atomic weapons

atomīˈzer or atomīˈser noun

An instrument for discharging liquids in a fine spray

atˈomy noun (archaic)

1. An atom, or mote
2. A pygmy (Shakespeare)

atom bomb or atomic bomb noun

A nuclear device in which quantities of uranium-235 or plutonium are forced to become critical with the result that their nuclei are bombarded by neutrons and split with explosive transformation of part of their mass into energy

atomic clock noun

A clock in which, to achieve greater accuracy, the oscillations of a quartz crystal (qv) are regulated by the vibration of certain atoms such as a caesium atom

atomic energy noun

Nuclear energy

atomic mass unit noun

1/12 of the mass of an atom of carbon-12

atomic number noun

The number of units of charge of positive electricity on the nucleus of an atom of an element

atomic philosophy noun

A system of philosophy enunciated by Democritus, which taught that the ultimate constituents of all things are indivisible particles, differing in form and in their relations to each other

atomic pile noun

An early name for a device for the controlled release of nuclear energy, eg a lattice of small rods of natural uranium embedded in a mass of pure graphite which serves to slow down neutrons

atomic power, atomic radiator see atomic above.

atomic second noun

A time interval whose measurement uses the frequency of radiation emitted or absorbed during transition from one energy state to another of a chosen atom

atomic theory noun

The hypothesis that all atoms of the same element are alike and that a compound is formed by union of atoms of different elements in some simple ratio

atomic time noun

Time whose unit is the atomic second

atomic transmutation noun

The change of one type of atom to another as a result of a nuclear reaction

atomic volume noun

The atomic weight of an element divided by its density

atomic warfare noun

Warfare using atomic weapons

atomic weight noun

Relative atomic mass (qv under relate)

aˈtom-smasher noun (informal)

An apparatus for breaking up the atom, an accelerator

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• exon
• Exon.
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