Definition of Atom

(v. t.)
To reduce to atoms.
  

(n.)
The smallest particle of matter that can enter into combination; one of the elementary constituents of a molecule.
  

(n.)
Anything extremely small; a particle; a whit.
  

(n.)
An ultimate particle of matter not necessarily indivisible; a molecule.
  

(n.)
An ultimate indivisible particle of matter.
  

(n.)
A constituent particle of matter, or a molecule supposed to be made up of subordinate particles.
  

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atom
\at"om\ (&?;), n. [l. atomus, gr. &?;, uncut, indivisible; 'a priv. + &?;, verbal adj. of &?; to cut: cf. f. atome. see tome.]
1. (physics) (a) an ultimate indivisible particle of matter. (b) an ultimate particle of matter not necessarily indivisible; a molecule. (c) a constituent particle of matter, or a molecule supposed to be made up of subordinate particles.
note: these three definitions correspond to different views of the nature of the ultimate particles of matter. in the case of the last two, the particles are more correctly called molecules.
2. (chem.) the smallest particle of matter that can enter into combination; one of the elementary constituents of a molecule.
3. anything extremely small; a particle; a whit. there was not an atom of water. ross.
atom
\at"om\, v. t. to reduce to atoms. [obs.] [
atom
n
1. (physics and chemistry) the smallest component of an element having the chemical properties of the element
2. (nontechnical usage) a tiny piece of anything [syn: molecule, particle, mote, speck]

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  similar words(4) 

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 rutherford atom 
 atom-bomb 
 vortex atom 
 unsymmetrical carbon atom 

adamh

Mymryn = n. an atom

  moat

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Noun
1. (physics and chemistry) the smallest component of an element having the chemical properties of the element
(hypernym) substance, matter
(hyponym) isotope
(part-holonym) chemical element, element
(part-meronym) elementary particle, fundamental particle, subatomic particle
(derivation) atomize, atomise
(classification) physics, physical science, natural philosophy
2. (nontechnical usage) a tiny piece of anything
(synonym) molecule, particle, corpuscle, mote, speck
(hypernym) material, stuff
(hyponym) grain
(derivation) atomize, atomise

the smallest quantity of an element capable of either entering into a chemical combination or existing alone.

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atom, atomic structure (proton, neutron, electron): "The smallest physical unit of a chemical element that can still retain all the physical and chemical properties of that element. Atoms combine to form molecules, and they themselves contain several kinds of smaller particles. An atom has a dense central core (the nucleus) consisting of positively charged particles (protons) and uncharged particles (neutrons). Negatively charged particles (electrons) are scattered in a relatively large space around this nucleus and move about it in orbital patterns at extremely high speeds. An atom contains the same number of protons as electrons and thus is electrically neutral (uncharged) and stable under most conditions. "

 Say it 
Compare with molecule and ion .An atom is the smallest particle of an element that retains the chemical properties of the element. Atoms are electrically neutral, with a positively charged nucleus that binds one or more electrons in motion around it.

The smallest particle of an element that cannot be divided or broken up by chemical means. It consists of a central core of protons and neutrons, called the nucleus. Electrons revolve in orbits in the region surrounding the nucleus.

The smallest unit of an element consisting of a dense positively charged nucleus (of protons and neutrons) orbited by negatively charged electrons.

is the smallest unit of a chemical element that can take part in a chemical reaction. An atom :is composed of a nucleus containing protons and neutrons, and :is surrounded by electrons. AVHRR stands for Advanced Very High Resolution Radiometer, the imagery produced by NOAA (National Oceanographic and Atmospheric Admin:istration) satellites. Pixel size is 1km x 1km for local area coverage (LAC) and 2km x 2km for global area coverage (GAC).

A tiny particle of matter made up of electrons , protons and neutrons. Atoms or combinations of atoms make up molecules. The electrons orbit around the center or nucleus made up of the protons and neutrons.

The smallest complete particle of an element, which can be obtained, yet which retains all physical and chemical properties of the element.

The smallest unit matter can be divided into whilst still retaining its chemical identity. Atoms are not single particles but complex arrangements of three types of particles. The subatomic particles, protons, neutrons and electrons, combine to form atoms. The protons and neutrons provide the bulk of an atom's mass and are concentrated into a tiny central region known as the atomic nucleus. The nucleus is held together by the strong nuclear force which acts between the constituent particles (termed nucleons ). The protons are positively charged and so mutually repel each other, but it is not until there are many of them that they overcome the nuclear force. Thus there is only one stable element beyond lead (Z=82). Whilst the radius of an atom is in the region of 10^-10 metres, the atomic nucleus is about ten thousand times smaller at 10^-14 metres. The volume surrounding the nucleus is where the electrons exist. They are much lighter than the protons and neutrons and carry a negative electrical charge. Being opposite in charge to the nucleus, the electrons are held in orbits around it by the force of electromagnetism. The electrons exist in electron orbitals around the nucleus. These orbitals are grouped into shells. Within each shell are energy levels which allow the electrons to exist in unique quantum states, depending upon their angular momentum (hence energy), in accordance with Pauli's exclusion principle . In a neutral atom the number of electrons equals the number of protons. When ionisation occurs, one or more electrons are provided with enough energy to escape the atom altogether. What remains is known as an ion because it is now positively charged and will behave in a different way chemically from neutral atom. The number of protons in the nucleus of an atom (the atomic number , Z) defines which chemical element it is. There are just over 110 known chemical elements and these can be arranged in a classification sequence known as the periodic table. The number of neutrons in any given atomic nucleus can also vary. The total number of protons + neutrons is termed the atomic mass number (A). Most atoms have a prefered number of neutrons at which their nuclei are stable. Atoms with more or less neutrons than the stable configuration are known as isotopes and will often undergo radioactive decay. The simplest of all atoms is hydrogen and is a special case which has a nucleus of one solitary proton and a single electron in orbit around it. It is the only nuclide (species of nucleus) with no neutron. A stable isotope of hydrogen is called deuterium which has one neutron in its nucleus; tritium is an unstable (radioactive) isotope of hydrogen and has two neutrons. See also atomic absorption , atomic emission , atomic number , molecule .

Formed by a nucleus of positively charged protons and neutral neutrons, with negatively charged electrons orbiting the nucleus.

the smallest particle that can exist and still exhibit the properties of an element.

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The smallest unit of matter that is unique to a particular element. They are the ultimate building blocks for all matter.

galu

Atom atomos (Greek) Indivisible, individual, a unit; among the Greek Atomists what in theosophy is called a monad. Atomic theories of the constitution of the universe or of matter are many and ancient. In modern physics the atom is a small particle once thought indivisible, but now resolved into component units. In some philosophies, as that of Leibniz, the atoms (which he calls monads) are psychological rather than physical units -- unitary beings of diverse kinds and grades, composing the universe.
In theosophy, atoms have to be considered in relation to monads; in The Secret Doctrine gods, monads, and atoms are a triad like spirit, soul, and body. A monad is a divine-spiritual life-atom, a living being, evolving on its own plane, and a life-atom is the vehicle of the monad which ensouls it, and in turn ensouls a physical atom. The ultimates of nature are atoms on the material side, monads on the energic side; monads are indivisible, atoms divisible (a departure from the etymological meaning). Thus there is a quaternary of gods, monads, life-atoms, and physical atoms. "An atom may be compared to (and is for the Occultist) the seventh principle of a body or rather of a molecule. The physical or chemical molecule is composed of an infinity of finer molecules and these in their turn of innumerable and still finer molecules. Take for instance a molecule of iron and so resolve it that it becomes non-molecular; it is then, at once transformed into one of its seven principles, viz., its astral body; the seventh of these is the atom. The analogy between a molecule of iron, before it is broken up, and this same molecule after resolution, is the same as that between a physical body before and after death. The principle remains minus the body. Of course this is occult alchemy, not modern chemistry" (TBL 84).

A particle of matter composed of a nucleus surrounded by orbiting electrons.

 the smallest particle of an element that can enter into a chemical reaction.
  

the smallest division of an element that can exist independently. Atoms are made up of protons, neutrons and electrons, and are the component parts of molecules.