Atomic Thoeries!

Today we learned about many atomic thoeries throughout history. An atomic thoery relates idea/thoeries about small particles such as atoms, protons, and electrons.

These are some of the atomic thoeries we learned today:

Atomic Thoery	Main Features	Diagram	Shortcomings/Problems
Democritus 300 BC	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	Atom the indivisible particle Atomos (in ancient Greek) means "that which cannot be further broken down into smaller pieces".	Does not give a scientific view of the atom only a conceptual definition Does not talk about subatomic particles (Electrons, Protons, Neutrons)
John Dalton 1800s	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	The solid sphere model Atoms are seen as solid, indestructible spheres (like billiard balls)	Does not include the existence of the nucleus Does not explain the existence of ions or isotopes Does not talk about subatomic particles (Electrons, Protons, Neutrons)
J.J. Thompson 1850s	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	The raisin bun Model or the chocolate chip cookie model : Atoms are solid spheres made-up of a solid positive mass (or core) with tiny negative particles embedded in the positive core.	Does not explain the existence of electrons outside the nucleus does not explain the role of electrons in bonding Does not talk about neutrons therefore can't explain radioactivity and the existence of isotopes
Rutherford 1905	First real modern view of the atom Explains why the electron spins around the nucleus Proposes that the atom is really mostly empty space	The Planetary Model Famous Gold Leaf Experiment proves that the nucleus is positive and the electrons are outside the nucleus.	Does not place electrons in definite energy levels around the nucleus Doesn't include neutrons in the nucleus Does Not relate the valence electrons atomic charge
Neils Bohr	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	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.	It does not explain the shapes of molecules or other abnormalities that result form unevenly shared pairs of electrons (such as the abnormal behaviour of water, the difference in Carbon-Carbon Bonds between diamond and graphite etc..)