1. The Development of Atomic Theory

2. 10.1 The Nature of Matter
Matter is a term used to describe anything that has mass and takes up space.
Greek philosophers Democritus and Leucippus proposed that matter is made of tiny particles called atoms.
Atoms were an idea that few believed.
The first evidence was called Brownian motion for Robert Brown, who first noticed the jerky motion of tiny particles.(1827)

3. Atom from the Greek word atomos that means indivisible
Democritus
Atom from the Greek word atomos that means indivisible

4. Democritus
Proposed that all atoms are small hard particles made of a single material
Different shapes and sizes
Atoms are always moving
They form different materials by joining together

5. John Dalton(1803) All substances are made of atoms.
Atoms are small particles that cannot be created, divided, or destroyed.
Atoms of the same element are exactly alike (1803)
The solid sphere model - like a sour ball

6. An early model
In 1897 English physicist J. J. Thomson discovered that electricity passing through a gas caused the gas to give off particles that were too small to be atoms.
These negative particles were eventually called “electrons.”

7. Plum –Pudding Model-Chocolate Chip Cookie Model
The atom is mostly positively charged material.
Electrons are small, negatively charged particles located throughout the positive material.
Proved atoms can be divided into smaller parts

8. Ernest Rutherford Designed an experiment to test Thomson’s theory.
Proposed that in the center of the atom is a tiny dense positively charged region called the nucleus.
Tootsie roll pop

9. Rutherford’s Gold Foil Experiment
He aimed a beam of small positively
charged particles at a sheet of gold foil.The particles were larger than protons.

10. The nuclear model
In 1911, Ernest Rutherford, Hans Geiger, and Ernest Marsden did a clever experiment to test Thomson’s model.
We now know that every atom has a tiny nucleus, which contains more than 99% of the atom’s mass.

11. Bohr’s Model of the Atom
Electrons travel in definite paths around the nucleus. These paths are located in levels at certain distances from the nucleus
Gob stopper model

12. Bohr Model
A Planetary Model of the Atom
                                                                                

13. Erwin Schrodinger and Werner Heisenberg
Ferrero Rocher Model
They explained the nature of electrons in an atom

14. Electrons and the Periodic Table
Order of filling levels

15. Energy levels
These levels are divided into smaller regions called orbitals.
These regions are designated by the following letters
s,p,d and f

16. Orbitals s- can hold 2 electrons p- can hold 6 electrons
d- can hold 10 electrons
f- can hold 14 electrons

17. Orbitals The Atomic Orbitals Atom in a Box
Real-Time Visualization of the Quantum Mechanical Atomic Orbitals
The orbital images on this page represent the shape of the atomic orbitals. The clouds you see are the probability distribution of an electron bound to a Hydrogen nucleus.
                                              

18. The Modern Atomic Theory
Electrons do not travel in definite paths as Bohr had suggested
The exact path of a moving electron cannot be predicted.
Electron clouds are regions inside the atom where electrons are likely to be found

19. 10.1 Atoms
A single atom is the smallest particle that retains the chemical identity of the element.

20. 10.1 Molecules
A molecule is a group of two or more atoms joined together chemically.