April 14 2011

Sup Wes here putting mah name in all the blogs I do from now on. Learned some atomic theory today, some pretty interesting stuff, I suppose.... So in chemistry, atomic theory is a theory of the nature of matter, which states that matter is composed of discrete units called atoms, as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity. It began as a philosophical concept in ancient Greece (Democritus) and India and entered the scientific mainstream in the early 19th century when discoveries in the field of chemistry showed that matter did indeed behave as if it were made up of particles.

I made a little something, something to help explain the different atomic theories.

Scientist and date	Name of model/Idea of theory	Importance/Improvement from last model
Democritus 300 BC	Atom the indivisible particle	Talks about the atom as the smallest particle of matter. Defines the atom as an indivisible particle Explains certain natural occurrences such as the existence of elements
Dalton 1800	The solid sphere model Atoms are seen as solid, indestructible spheres	Explains a lot of chemical properties such as how atoms combine to form molecules Explains chemical change better than the Particle Theory Confirms the basic Laws of Chemistry: Conservation of Mass & definite Proportions
J.J. Thomson 1850	The raisin bun Model Atoms are solid spheres made-up of a solid positive mass (or core) with tiny negative particles embedded in the positive core.l	Infers on the existence of electrons and protons Introduces the concept of the nucleus Infers on the relative nuclear density and atom mass of different atoms
Rutherford 1905	The Planetary Model Gold leaf experiment proves that the nucleus is positive and the electrons are outside the nucleus.	First real modern view of the atom Explains why the electron spins around the nucleus (Bohr's Contribution)
(Neils Bohr) Bohr- Rutherford 1920	Electrons in Definite energy Levels around the nucleus Used atomic spectra to prove that electrons are placed in definite orbitals (called shells) around the nucleus.	Explains the role of valence electrons in bonding Relegates the number of valence electrons to the Periods of a periodic table Fully explains ionic and covalent bonding Places electrons in definite energy levels 2 e^- in the first 8 e^- in the second 8 e^- in the third