Atom definition

The smallest unit of an element, consisting of at least one proton and (for all elements except hydrogen) one or more neutrons in a dense central nucleus, surrounded by one or more shells of electrons. In electrically neutral atoms, the number of protons equals the number of electrons. Atoms remain intact in chemical reactions except for the removal, transfer, or exchange of certain electrons.

(obs.) Any of the indivisible particles postulated by philosophers as the basic component of all matter.

The smallest unit of an element, having all the characteristics of that element and consisting of a very small and dense central nucleus containing protons and neutrons, surrounded by one or more shells of orbiting electrons. Atoms remain undivided in chemical reactions except for the donation, acceptance, or exchange of valence electrons.

The irreducible, indestructible material unit postulated by ancient atomism.

This unit regarded as a source of nuclear energy.

(chem., physics) Any of the smallest particles of an element that combine with similar particles of other elements to produce compounds: atoms combine to form molecules, and consist of a complex arrangement of electrons revolving about a positively charged nucleus containing (except for hydrogen) protons and neutrons and other particles.

An atom includes a nucleus, and then a series of orbital circles that surround this nucleus similar to the solar system structure.

The protons and the neutrons reside in the nucleus.

The electrons are in the orbitals.

The amount of protons in the nucleus of an atom determines its atomic number.

An extremely small part, quantity, or amount.

A part or particle considered to be an irreducible constituent of a specified system.

A tiny particle of anything; jot.

The definition of an atom is the smallest component of an element, characterized by a sharing of the chemical properties of the element and a nucleus with neutrons, protons and electrons.