SECTIONS

General Stuff/Energy and Matter

Atomic Structure

Electron Configuration & The Periodic Table

Chem Formulas and Bonding & Molecular Shape

Chemical Reactions and Equations, heat, and Gas laws

Section 3: Atomic Structure

Democratus- came up with the concept of breaking things in half until you finally come up with the smallest particle
John Dalton- came up with the idea that the atoms of a different element are different, and that compounds come in fixed proportions of atoms

The Atom-
Atomic Theory of Matter:
-Each element is composed of small particles- atoms
-All atoms from a given element are identical, but they differ from those of any other element
-Atoms aren’t created or destroyed (Lavoiser)
-Each compound has the same relative #s and kinds of atoms
Michael Faraday- discovered that atoms have charges. Franklin proved this with the lightning experiment: the two charges attract each other but repel others of their own kind
Electric Current- a moving string of electrons
Cathode ray tube- partially evacuated air tube containing a cathode (-) and an anode (+), and lined with fluorescent material. It allows us to see the radiation. For more info, turn to your book, page 97.
Radioactivity- the spontaneous emission of radiation from an element. This was discovered by Bequerel, who put uranium on photographic paper and saw that it exposed the paper.
The first model of the atom was the Plum Pudding model. It was that there was negative charges (plums) tossed into a pudding of positive charge.

Rutherford disproved this by doing an alpha- scattering experiment in which he shot helium electrons at thin gold foil.

Rutherford’s experiment showed that the nucleus is very dense and little negatively charged electrons existed around the small nucleus. The nucleus was positively charged. Rutherford was right! (so far, he hasn’t been disproven, so we’re just assuming)

Here’s an atom:

Proton: positively charged, located in nucleus
Electron: negatively charged, spins around the nucleus (represented by the black). Very light
Neutron: weighs almost the same as proton. Located in the nucleus. Neutrally charged.

Atoms and The Periodic Table-
We will often refer to the Periodic Table of the Elements in the back of your book. It looks kinda like this:

Atomic number: distinct number of protons in each element
Ion- the net electrical charge that occurs when electrons are lost or gained in a reaction. This net charge can be figured using (the number of protons) – (the number of electrons)
Mass number, or AMU: the weight of the element. This is the number of protons + the number of neutrons. The one shown on the periodic table is an average for that element.
Isotope- just an atom with a different mass # than all the rest. They still have the same chemical properties, though. Some isotopes are more common than others. Like saying “Carbon-13”. If a Carbon atom with 13 as an atomic mass ever existed, it would be an isotope, because most Carbon atoms have 12 a their mass number.