2.1: Atomic Theory

ATOMS, MOLECULES (COMPOUNDS), IONS

ATOMIC THEORY

*Development of Atomic Structure

*Indivisible Particle - atomos -atom

1800's: Dalton - Thought Process

1. Elements are made up of all the same kinds of atoms.

2. The smallest particle of a n element is atom.

3. Law of conservation of mass: Atoms are not created or destroyed in a chemical reaction. That is the total mass of the products must equal of that of the reactants. Example:

4. Law of Definite Proportions: Atoms combine in whole number ratios to form compounds. Example:

Water (H2O) = 11.2% Hydrogen, 88.8% Oxygen 

Peroxide (H2O2) = 5.9% Hydrogen, 94.1% Oxygen 

5. Law of Multiple Proportions: If atoms combine in different ratios, they form different compounds. Example: 
CO2 vs. CO

DISCOVERY OF THE ATOM

(Through Experimentation)

Thomson - 1897 - Discovery of the electron (e-)

--> (charge/mass) ratio of the electron

Millikan - 1909 - "Oil drop experiment"

--> Charge of the e-

--> mass of the e-

Rutherford - 1919 - Gold Foil

--> Existence of atomic nucleus

 MODERN ATOMIC STRUCTURE: Bohr Model

Subatomic Particles:

PROTONS	ELECTRONS	NEUTRONS
Positive charge            (+) P = 1.0073 amu	Negative charge             (-) e = 5.49x10⁻⁴ amu	Neutral charge            (0) n = 1.0087 amu

Note:

1 amu = 1.66 x 10⁻²⁴

Mass of an atom: 10⁻²²