1. Chapter 5
The ATOM
Democritus (400 BC) reasoned that all things were made up of indivisible particles: ATOMS
Dalton ( ) performed experiments
Atomic Theory
All elements are composed of tiny indivisible particles called ATOMS
Atoms of the same element are identical, but different from other elements
Atoms of different elements can physically or chemically combine in whole number ratios
Chemical reactions occur when atoms are joined, separated, or rearranged. But atoms of one element ae never changed into atoms of another element.

2. Atoms are really, really small
A copper coin has about 2.4 x 10^22 atoms
24,000,000,000,000,000,000,000 atoms

3. Atomic Structure
Electrons (JJ Thompson 1897)
-negative charge
-Millikan calculated the weight and charge of the electron in 1916
Protons and Neutrons
-Protons (Goldstein 1886)are Positive and about times the size of an electron
-Neutrons (Chadwick 1932) are Neutral and have about the same weight as a proton
Rutherford 1911: Most of an atom is empty space, positive charge centered in the nucleus

4. Atomic Number On the periodic table
Tells number of protons and electrons
Mass Number
-On the periodic table
-unit = AMU (atomic mass units)
-Number of protons + neutrons
-to find the number of neutrons,
MASS NUMBER – ATOMIC NUMBER

5. Isotopes
Atoms that have the same number of protons, but different numbers of neutrons are called ISOTOPES
Will have same ATOMIC NUMBER, but different MASS NUMBER
Example: Carbon-12 and Carbon-14
Both have an atomic number of 6, but the mass numbers are different

6. Atomic Mass Most elements occur as a mixture of two or more isotopes.
The atomic mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element

7. Your Project
You are going to write a book to explain early atomic theory and structure to elementary children. Part one: Atomic Theory You must include: Dalton’s Atomic Theory, JJ Thompson, Rutherford, and Bohr. Part Two: Parts of the periodic table Where to find atomic symbol, mass, and number How to calculate the number of protons, neutrons, and electrons

8. Grading I am grading this for completion and ‘appearance’
For full credit, you MUST include all of the required pieces, the book must be neat and organized, and the information must be correct and clearly stated.
Opportunity for bonus: Go above and beyond? You’ll earn points on your midterm!