Question

definition of an atom.
answer in long.
and answer urgent please

Answer 1

atom definition. A unit of matter; the smallest unit of a chemical element. Each atom consists of a nucleus, which has a positive charge, and a set of electrons that move around the nucleus. (See Bohr atom.) 
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Answer 2

Hey friend

Here is your answer

Atoms are the basic building blocks of ordinary matter. Atoms can join together to form molecules, which in turn form most of the objects around you.

Atoms are composed of particles called protons, electrons and neutrons. Protons carry a positive electrical charge, electrons carry a negative electrical charge and neutrons carry no electrical charge at all. The protons and neutrons cluster together in the central part of the atom, called the nucleus, and the electrons 'orbit' the nucleus. A particular atom will have the same number of protons and electrons and most atoms have at least as many neutrons as protons.

Protons and neutrons are both composed of other particles called quarks and gluons. Protons contain two 'up' quarks and one 'down' quark while neutrons contain one 'up' quark and two 'down' quarks. The gluons are responsible for binding the quarks to one another.

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