1. Unit 3: Elements, Compounds, and Reactions HISTORY OF THE ATOM

2. Democritus – 400 BC Greek philosopher
1st person to develop atomic theory
matter can be broken down so far and no further – called this particle “atomos”
Atoms are like a solar system, mostly made of empty space.

3. John Dalton – Late 1700s
Developed the atomic theory on which all current understandings of the atom are based.
The atom is spherical.
In a chemical reaction, atoms cannot be created or destroyed but can be rearranged.
Each element has its own atom which differs from others

4. Dmitri Mendeleev - 1869 Russian chemist
Arranged the 63 known elements into groups and periods and called it the Periodic Table of Elements.
His understanding of chemical properties and atomic weights allowed him to leave spaces for undiscovered elements.

5. J.J. Thomson – 1890s
Discovered the electron (negatively charged particle)
Proposed the “Plum Pudding” model of the atom.
Did many experiments which led him to believe in the existence of an atomic particle “with a mass about 1,000 times smaller than a hydrogen atom.”
Did not have support of his colleagues, which made him work harder to prove that the electron existed.

6. Ernest Rutherford
Discovered the proton (a positively charged particle)
Developed the idea of the nucleus (center) of the atom and said it has a positive charge.
Proposed the idea of another particle, the neutron (no charge).
Found that the particles was found in a specific location relative to one another.

7. Neils Bohr s
Proposed the first model of the atom to gain acceptance.
Electrons orbit the nucleus in fixed energy levels aka orbitals.
1st energy level holds 2 electrons
2nd energy level holds 8 electrons
3rd energy level holds 8 or 18 electrons

8. James Chadwick
Credited with the discovery of the neutron (a neutrally charged particle).
His discoveries resulted from learning from others such as Frederic and Irene Joliot-Curie and Ernest Rutherford.
Discovered that the mass of the neutron was about 0.1 percent more than the proton’s.

9. Erwin Schrodinger - 1933 Each electron shell is made up of subshells.
Subshells can be further divided into orbitals.
Used Quantum Mechanics to locate electrons.

10.
Neils Bohr informed the U.S. of the latest development of Nazi Germany, the splitting of the atom.
President F. Roosevelt established the Manhattan project where the best minds in physics developed the atomic bomb.

11. FLOW MAP RUBRIC Name, date, subject, hour = ____/4 points
Title for flow map “History of the Atom” = ____/1 points
Information is in correct sequence = ___/10 points
Neat, colorful and complete = 5 points
Construct 9 boxes = ____/9 points
In each box
Name of scientist/group ____/1 point
Date of discovery ____/ 1 point
Discovery ____/2 points
TOTAL = _____/65 points