Section 3-1: Main Ideas
 TEKS: 2C, 2H, 3E, & 6A
 Explain the law of conservation of mass, the law of definite proportions, and the law of multiple proportions.
 Summarize the five essential points of Dalton’s atomic theory.
 Explain the relationship between Dalton’s atomic theory and the law of conservation of mass, the law of definite
proportions, and the law of multiple proportions.
Democritus (400 BCE)
Believed in atoms; indivisible
“atmos” – cannot cut
Aristotle
Did not believe in atoms
Believed in:
Air, earth, fire, & water
Vocabulary
 Law of Conservation of Mass:
 Law of Definite Proportions:

Law of Multiple Proportions:
Matter cannot be created nor destroyed.
A compound will always have the same elements in the same ratio by
mass.
Elements combine with other elements to form different compounds in
whole number ratios.
John Dalton (1803) - Billiard Ball Model
1. Elements are made of tiny, indestructible particles called atoms. (Democritus)
2. All atoms of the same element are identical and have the same properties.
3. Atoms of different elements combine in small whole number ratios to form compounds.
(Law of Definite Proportions, Proust)
4. Atoms may combine in more than one ratio to form different compounds.
(Law of Multiple Proportions)
5. In a chemical reaction, atoms are rearranged; nothing is created nor destroyed.
(Law of Conservation of Mass, Lavoisier)
Section 3-2: Main Ideas
 TEKS: 6A
 Atoms contain positive and negative particles.
 Atoms have small, dense, positively charged nuclei.
 A nucleus contains protons and neutrons.
 Summarize the experiment carried out by Rutherford and his co-workers that led to the discovery of the
nucleus.
 List the properties of protons, neutrons, and electrons.
Sir Joseph John Thomson (1897) - Plum-pudding Model
 Discovered the electron
 Cathode Ray Tube Experiments
Robert Millikan (1909)
 Discovered the mass of the electron.
 Verified the charge of the electron.
Ernest Rutherford (1911) – Nuclear Model
 Discovered the nucleus
 Gold foil experiment-Geiger & Marsden
Niels Bohr(1913) – Planetary Model
 Electrons in orbits
Ernest Rutherford (1919)
 Discovered the Proton.
James Chadwick (1922)
 Discovered the neutron
Vocabulary
 Atom
 Nuclear forces
Section 3-3: Main Ideas
 TEKS: 6D, 8A & 8B
 Explain what ions are.
 Explain what isotopes are.
 Define atomic number and mass number, and describe how they apply to isotopes.
 Given the identity of a nuclide, determine its number of protons, neutrons, and electrons.
 Define mole in terms of Avogadro’s number, and define molar mass.
 Be able to calculate molar mass of an element/compound.
 Solve problems involving mass in grams, amount in moles, and number of atoms of an element.
 Perform conversion between Moles
Mass and Moles
Particles.
Vocabulary
 Atomic Number (Z)
 Atomic Mass Number (A)
 Ions
 Isotopes
 Nuclides
 AMU
 Relative Atomic Mass
 Average Atomic Mass
 Mole
 Avogadro’s Number
Protons
 Positive particle found in nucleus
 Mass of 1
Electrons
 Negative particle found in electron cloud
 Mass of 1/1836
Neutrons
 Neutral particle found in nucleus
 Mass of 1
Atomic Symbol Notation
𝐴
𝑍𝑋
 “A” Atomic Mass Number
 “Z” Atomic Number
Hyphen Notation
Element Name-Atomic Mass Number (A) ex. Oxygen-16