Chem 134 chapters 1-3

Fundamental Concepts of Atomic Theory

Dalton's Atomic Theory

• Proposed that all matter is composed of tiny, indivisible particles called atoms.

• Atoms cannot be created or destroyed, aligning with the law of conservation of mass.

• Introduced the idea that atoms of a given element are identical in mass and properties.

• The theory laid the groundwork for modern chemistry and the understanding of chemical reactions.

• Dalton's work was pivotal in the early 19th century, marking a significant shift in scientific thought.

Laws of Chemical Composition

• Law of Definite Proportions: All samples of a given compound have the same proportions of their constituent elements.

• Law of Multiple Proportions: When two elements form two different compounds, the ratios of the masses of one element that combine with a fixed mass of the other can be expressed as small whole numbers.

• These laws highlight the predictable nature of chemical combinations and reactions.

Key Experiments in Atomic Theory

• Cathode Ray Experiment: Conducted by J.J. Thomson, this experiment led to the discovery of the electron, demonstrating that atoms contain smaller particles.

• Millikan's Oil Drop Experiment: Robert Millikan determined the charge of a single electron, providing a fundamental constant in physics.

• Rutherford's Gold Foil Experiment: Showed that atoms consist mostly of empty space with a dense, positively charged nucleus, revolutionizing the understanding of atomic structure.

Properties of Matter

Intensive vs. Extensive Properties

• Intensive Properties: Independent of the amount of substance present (e.g., density, boiling point, color).

• Extensive Properties: Depend on the amount of substance present (e.g., mass, volume, energy).

• Understanding these properties is crucial for characterizing materials and predicting their behavior in chemical reactions.

Classification of Compounds

• Hydrates: Ionic compounds that contain water molecules within their structure.

• Acids: Can be classified into binary acids (containing only two elements) and oxyacids (containing oxygen and a polyatomic ion).

• Naming conventions: For binary acids, the prefix 'hydro-' is used, and the suffix '-ic' is added to the root of the second element. Oxyacids are named based on the polyatomic ion (e.g., 'ate' becomes '-ic', 'ite' becomes '-ous').

Hydrocarbons and Their Structures

Types of Hydrocarbons

• Alkanes: Saturated hydrocarbons with single bonds (C-C).

• Alkenes: Unsaturated hydrocarbons with at least one double bond (C=C).

• Alkynes: Unsaturated hydrocarbons with at least one triple bond (C≡C).

• The structure of hydrocarbons determines their reactivity and physical properties.