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Ch.2 Atoms and the Periodic TableWorksheetSee all chapters
All Chapters
Ch.1 Matter and Measurements
Ch.2 Atoms and the Periodic Table
Ch.3 Ionic Compounds
Ch.4 Molecular Compounds
Ch.5 Classification & Balancing of Chemical Reactions
Ch.6 Chemical Reactions & Quantities
Ch.7 Energy, Rate and Equilibrium
Ch.8 Gases, Liquids and Solids
Ch.9 Solutions
Ch.10 Acids and Bases
Ch.11 Nuclear Chemistry
BONUS: Lab Techniques and Procedures
BONUS: Mathematical Operations and Functions
The Atom (Simplified)
Subatomic Particles (Simplified)
Ions (Simplified)
Atomic Mass (Simplified)
Atomic Mass (Conceptual)
Periodic Table: Element Symbols
Periodic Table: Classifications
Periodic Table: Group Names
Periodic Table: Representative Elements & Transition Metals
Periodic Table: Elemental Forms (Simplified)
Periodic Table: Phases (Simplified)
Law of Definite Proportions
Atomic Theory
Rutherford Gold Foil Experiment
Wavelength and Frequency (Simplified)
Electromagnetic Spectrum (Simplified)
Bohr Model (Simplified)
Emission Spectrum (Simplified)
Electronic Structure
Electronic Structure: Shells
Electronic Structure: Subshells
Electronic Structure: Orbitals
Electronic Structure: Electron Spin
Electronic Structure: Number of Electrons
The Electron Configuration (Simplified)
Electron Arrangements
The Electron Configuration: Condensed
The Electron Configuration: Exceptions (Simplified)
Ions and the Octet Rule
Ions and the Octet Rule (Simplified)
Valence Electrons of Elements (Simplified)
Lewis Dot Symbols (Simplified)
Periodic Trend: Metallic Character
Periodic Trend: Atomic Radius (Simplified)

"Different samples of a pure chemical compound always contain the same proportions of elements by mass."

Proust's Law of Definite Proportions

Concept #1: Law of Definite Proportions

Example #1: Two unknown compounds are examined. Compound A contains 2.0 grams of hydrogen and 32.0 grams of oxygen. Compound B contains 15.0 grams of hydrogen and 120.0 grams of oxygen. Do Compounds A and B represent the same compound?

Example #2: A compound contains only calcium and fluorine. A sample of the compound is determined to contain 2.00 g of calcium and 1.90 g of fluorine. According to the Law of Definite Proportions, how much calcium should another sample of this compound contain if it possesses 2.85 g of fluorine?

Practice: A 7.74 g sample of HCN is found to contain 0.287 g of H and 4.01 g N. Find the mass of carbon in a sample of HCN with a mass of 3.43 g.