Chemistry Chapter 3 Flashcards

Questions and Answers

What does the law of conservation of mass state?

Mass can be destroyed.

Mass is neither destroyed nor created during chemical or physical reactions. (correct)

Mass varies based on the size of the sample.

Mass is created during chemical reactions.

What is the law of definite proportions?

A chemical compound contains the same elements in exactly the same proportions by mass regardless of the size of the sample or source of the compound.

What does the law of multiple proportions state?

If two or more different compounds are composed of the same two elements, then the ratio of the masses of the second element combined with a certain mass of the first element is always a ratio of small whole numbers.

What is an atom?

The smallest unit of an element that maintains the properties of that element. Signup and view all the answers

Nuclear forces are short-range proton-neutron, proton-proton, and neutron-neutron forces that hold the nuclear particles together and are referred to as .

nuclear forces Signup and view all the answers

What is an atomic mass unit (amu)?

Exactly 1/12 the mass of a carbon-12 atom. Signup and view all the answers

What does the atomic number represent?

The number of protons in the nucleus. Signup and view all the answers

What is average atomic mass?

The weighted average of the atomic masses of the naturally occurring isotopes of an element. Signup and view all the answers

What is Avogadro's number?

6.022 x 10²³ Signup and view all the answers

What defines an isotope?

Atoms of the same element that have different masses. Signup and view all the answers

What is the mass number?

The total number of protons and neutrons in the nucleus. Signup and view all the answers

What is molar mass?

The mass of one mole of the substance, written in g/mol. Signup and view all the answers

What is a mole?

The SI unit for a substance; it is the amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12. Signup and view all the answers

What is a nuclide?

A general term for any isotope of any element. Signup and view all the answers

Match the following scientists with their contributions:

Thompson = Discovered electrons and found that the electron has a very large charge for its tiny mass. Millikan = Found the exact mass of the electron and confirmed its negative charge. Rutherford = Discovered that the nucleus is a very small positively charged region inside an atom. Democritus = Thought the atom was the basic particle and indivisible. Signup and view all the answers

What was the gold foil experiment?

A thin piece of gold foil was bombarded with alpha particles, and it was found that about 1 in 8000 were redirected back towards the source. Signup and view all the answers

What is a cathode?

The metal disk connected to the negative terminal of the voltage source. Signup and view all the answers

What is an anode?

The metal disk connected to the positive terminal of the voltage source. Signup and view all the answers

What did investigators notice during the cathode ray experiment?

When a current was passed through a cathode-ray tube, the surface of the tube directly opposite the cathode glowed. Signup and view all the answers

What did Aristotle believe about atoms?

He did not believe in atoms and thought all matter was continuous. Signup and view all the answers

What is a chemical reaction?

The transformation of a substance or substances into one or more new substances. Signup and view all the answers

What is the nucleus of an atom?

A very small region located near the center of the atom that contains at least one proton and usually at least one neutron. Signup and view all the answers

Define a neutron.

A neutrally charged atom. Signup and view all the answers

Define a proton.

A positively charged atom. Signup and view all the answers

Define an electron.

A negatively charged atom. Signup and view all the answers

What are subatomic particles?

Neutrons, electrons, and protons. Signup and view all the answers

What are alpha particles?

Positively charged particles with 4 times the mass of hydrogen. Signup and view all the answers

Why did they expect the alpha particles to pass straight through the gold foil?

They thought the mass was distributed evenly throughout the atom. Signup and view all the answers

What is hyphen notation?

The mass number separated with a dash after the name of the element (e.g., uranium-235). Signup and view all the answers

What is a nuclear symbol?

The superscript indicates the mass number, and the subscript indicates the atomic number (e.g., 235/92). Signup and view all the answers

The number of neutrons is calculated by mass number - atomic number = ________.

number of neutrons Signup and view all the answers

Study Notes

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).

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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!