What is a atom? that a history
An atom is the basic building block of all things. So, the chair that you are sitting on is made of atoms as well as the book that you read in school. Scientists estimate that there are about 90 different kinds of atoms.
Within an atom, there are three parts: protons, neutrons, and electrons. Protons carry a positive electric charge, electrons carry a negative electric charge, and neutrons, as you might expect, carry no electric charge.
Protons and neutrons are within the center of the atom, which is called the nucleus. Electrons can be said to orbit the nucleus. One more important fact, there will be equal number of protons and electrons.
If we probe a little deeper, then we can say that protons and neutrons are made of smaller particles called quarks and gluons.
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 quarksand 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.