How do atoms form?
The current view is that atoms are made up of protons and neutrons (which in turn are made up of quarks and gluons) and electrons. The protons and neutrons are at the central core called the nucleus, and the electrons revolve around it, being held in orbit by the electromagnetic force between the negatively charged electrons and the positively charged protons in the central nucleus. It is very much like the solar system with the sun at the center and the planets revolving around it. They were formed right after the "Big Bang" when our known universe originated from pure energy some billions of years ago. The energy was converted to the elementary particles (quarks, gluons, leptons etc...) from which protons and neutrons were formed. From these, atoms of different elements were produced.
Arun Saha, Staff Scientist (Other answers by Arun Saha)