Foundations of Matter: Atomic Theory and Nuclear Reactions

Element

A pure substance consisting of one type of atom.

Compound

A substance formed from two or more elements chemically bonded.

Heterogeneous Mixture

A mixture with visibly different substances or phases.

Homogeneous Mixture

A mixture with a uniform composition throughout.

Distillation

Separation technique based on vaporization differences.

Filtration

Separation method using a filter to separate solids from liquids.

Chromatography

Separation technique based on component polarities.

Subatomic Particles

Particles smaller than atoms, including protons, neutrons, electrons.

Protons

Positively charged particles found in the nucleus.

Neutrons

Neutral particles in the nucleus, stabilizing it.

Electrons

Negatively charged particles orbiting the nucleus.

Atomic Number

Number of protons in an atom's nucleus.

Mass Number

Total number of protons and neutrons in an atom.

Isotopes

Atoms with the same protons but different neutrons.

Ions

Atoms that have gained or lost electrons, acquiring a charge.

Cations

Positively charged ions formed by losing electrons.

Anions

Negatively charged ions formed by gaining electrons.

Chemical Formula

Notation representing the composition of a compound.

Subscripts

Numbers indicating the quantity of atoms in a compound.

Superscripts

Numbers indicating the charge of an ion.

Coefficients

Numbers indicating how many molecules are present.

Average Atomic Mass

Weighted average of the atomic masses of isotopes.

Quantum Mechanical Model

Current model describing electron behavior in atoms.

Rutherford's Gold Foil Experiment

Experiment that discovered the atomic nucleus.

Wave Mechanical Model

Model describing electrons in complex paths around nucleus.

Separation Techniques

Methods used to separate components of mixtures.

Chemical Notation

System for representing chemical compounds and reactions.

Isotope

Atoms of the same element with different masses.

Atomic Mass Unit (amu)

Unit of mass used to express atomic masses.

Weighted Average

Average calculated considering the abundance of each isotope.

Contribution Calculation

Multiply isotope mass by its percentage abundance.

Nuclear Reaction

Change in nucleus involving protons and neutrons.

Chemical Reaction

Involves rearrangement of electrons, not nuclei.

Neutron to Proton Ratio (N:Z)

Ratio determining nuclear stability of an element.

Fission

Nucleus splits into smaller nuclei, releasing energy.

Fusion

Nuclei combine to form a larger nucleus.

Half-Life

Time for half of a radioactive sample to decay.

Radioisotope

Unstable atom that decays over time.

Radiation

Particles and waves emitted during nuclear decay.

Alpha Particle

Helium-4 nucleus with low penetrating ability.

Beta Particle

Electron emitted during neutron decay.

Positron

Antielectron emitted during proton decay.

Gamma Ray

High-energy photon with strong penetrating ability.

Nuclear Decay

Process by which unstable nuclei lose energy.

Nuclear Equation

Equation representing nuclear reactions, must be balanced.

Alpha Decay

Nucleus emits an alpha particle, decreasing mass.

Beta Decay

Nucleus emits a beta particle, increasing atomic number.

Electron Capture

Nucleus captures an electron, decreasing atomic number.

Positron Emission

Nucleus emits a positron, decreasing atomic number.

Decay Products

New elements formed from nuclear decay.

Stability Band

Region where nuclei are stable based on N:Z ratio.

Nuclear Instability

Condition leading to nuclear decay for stability.

Radium-226

Radioactive isotope with a half-life of 1599 years.

Radon-222

Radioactive isotope with a half-life of 3.824 days.

Copper Isotopes

Copper-63 and Copper-65 contribute to copper's average mass.