Chemistry Chapter 3 Flashcards

Fundamental Laws of Chemistry

• Law of Conservation of Mass: Mass is conserved during chemical and physical reactions; it cannot be created or destroyed.
• Law of Definite Proportions: A chemical compound has a constant composition by mass, regardless of sample size or source.
• Law of Multiple Proportions: When two elements form different compounds, the mass ratios of the second element combined with a fixed mass of the first element are simple whole numbers.

Atomic Structure

• Atom: The smallest unit of an element that retains its chemical properties.
• Atomic Number: Represents the number of protons in an atom's nucleus, defining the element.
• Mass Number: The total count of protons and neutrons in an atom's nucleus.
• Isotope: Atoms of the same element with varying masses due to differing neutron counts.

Particle Mass and Measurement

• Atomic Mass Unit (amu): Defined as 1/12 the mass of a carbon-12 atom.
• Average Atomic Mass: The weighted average of an element’s isotopes based on their natural abundance.
• Molar Mass: The mass of one mole of a substance, expressed in grams per mole (g/mol).
• Avogadro's Number: The number of particles in one mole of a substance, approximately 6.022 x 10²³.

Subatomic Particles

• Neutrons, Electrons, Protons: The three main types of subatomic particles; neutrons are neutral, protons are positively charged, and electrons are negatively charged.
• Nucleus: A small, dense region at an atom’s center, containing protons and usually neutrons.
• Nuclear Forces: Short-range forces that unite protons and neutrons within the nucleus.

Historical Perspectives on Atomic Theory

• Dalton's Atomic Theory: Basic principles include the belief that all matter is made of atoms, elements consist of identical atoms, and atoms combine in simple ratios. Original components also contained misconceptions about atom divisibility.
• Modern Atomic Theory: Acknowledges the divisibility of atoms into smaller particles and that isotopes of an element may exhibit different masses.
• Democritus: Proposed the concept of indivisible atoms as the fundamental building blocks of matter.
• Aristotle: Dismissed atomic theory, asserting that matter was continuous.

Key Experiments and Discoveries

• Thompson's Experiment: Identified the existence of electrons, showcasing their significant charge in comparison to mass.
• Millikan's Oil Drop Experiment: Measured the mass of an electron and confirmed its negative charge.
• Rutherford’s Gold Foil Experiment: Demonstrated that atoms have a dense, positively charged nucleus as alpha particles were deflected unexpectedly.

Chemical Changes and Reactions

• Chemical Reaction: A process where substances transform into new substances through rearrangement of atoms.
• Cathode Ray Experiment: Revealed that cathode rays are composed of negatively charged particles.
• Alpha Particles: Positively charged particles, each with four times the mass of a hydrogen atom.

Nomenclature and Symbols

• Hyphen Notation: Indicates isotopes using the format "element-mass number" (e.g., uranium-235).
• Nuclear Symbol: Utilizes a superscript for mass number and a subscript for atomic number to represent isotopes (e.g., ²³⁵/₉₂ U).

Calculation of Neutrons

• Number of Neutrons: Calculated by subtracting the atomic number from the mass number (mass number - atomic number).

Test your knowledge with these flashcards on key concepts from Chemistry Chapter 3. This quiz covers fundamental laws such as the law of conservation of mass, law of definite proportions, and law of multiple proportions. Perfect for reviewing essential chemistry principles!