Atoms are the fundamental building blocks of matter. John Dalton proposed his atomic theory in 1808 which stated that elements are composed of tiny, indivisible atoms. Atoms of the same element are identical but different from atoms of other elements. Atoms combine in whole number ratios to form molecules. Subatomic particles like electrons, protons, and neutrons were discovered inside the atom. The nucleus contains protons and neutrons and is much smaller than the overall diameter of the atom.

1. Chapter 4 Atoms and Elements

3. Atomic Theory of Matter The belief that atoms are the fundamental building blocks of matter was reemerged in the early 19th century, championed by John Dalton.

5. Modern structure of the atom Subatomic Particle Symbol Electron e- Proton p Neutron n

8. Rutherford’s model of the atom http://highered.mcgraw-hill.com/sites/0072512644/student_view0/chapter2/animations_center.html -

9. In 1932 Chadwick observed that beryllium, when bombarded by alpha particles, released an unknown radiation that was neutral. Chadwick interpreted this radiation as being composed of particles of mass approximately equal to that of the proton, but without electrical charge--neutrons. The Neutron