History of the atom
Around 460 B.C., a Greek philosopher, Democritus, develop the idea of atoms. He asked this question: If you break a piece of matter in half, and then break it in half again, how many breaks will you have to make before you can break it no further?
Democritus thought that it ended at some point, a smallest possible bit of matter. He called these basic matter particles, atoms.
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As time progressed, there had been many models to show how the structure of the atom as seen below.
Let us see some of these models.
The atom... a pudding?
In the 1800's an English chemist, John Dalton performed experiments with various chemicals that showed that matter, indeed, seem to consist of elementary lumpy particles (atoms). Although he did not know about their structure, he knew that the evidence pointed to something fundamental.
JJ Thomson, who discovered the electron in 1897, proposed that the atom is like a plum pudding where electrons are surrounded by positive charges to balance the electrons' negative charges.
Accepted model of an atom - Bohr's model
The model that we use today was proposed only in 1913 by Niels Bohr. The atom is actually a small positively charged nucleus surrounded by electrons travelling in circular paths called electron shells.
The attraction between the nucleus and electrons are due to electrostatic forces.