Video Notes: Atomic Theory and Unit Conversions (Vocabulary Flashcards)

Vocabulary flashcards covering key terms and definitions from the lecture notes on unit conversions, atomic theory, isotopes, and basic nuclear chemistry.

Atom

The basic unit of an element, composed of a tiny nucleus of protons and neutrons with electrons surrounding it; Dalton’s idea that atoms are indivisible and unique to each element is the historical view, later refined by isotopes.

Isotope

Variants of the same element that have the same number of protons but different numbers of neutrons, leading to different mass numbers.

Atomic number (Z)

The number of protons in an atom’s nucleus; determines the element and its identity.

Mass number (A)

The total number of protons and neutrons in the nucleus; used in isotope notation.

Electron

Negatively charged subatomic particle located outside the nucleus; very small mass compared with protons and neutrons.

Proton

Positively charged subatomic particle in the nucleus; mass about 1 amu.

Neutron

Electrically neutral subatomic particle in the nucleus; contributes to atomic mass.

Ion

An atom or molecule with a net electric charge due to gain or loss of electrons.

Cation

A positively charged ion formed when electrons are removed from an atom.

Anion

A negatively charged ion formed when electrons are gained by an atom.

Millikan (oil drop) experiment

Experiment that measured the electric charge of the electron, enabling determination of e.

Thomson (cathode ray) experiment

Experiment that discovered the electron and determined its negative charge and its relation to mass (e/m).

Rutherford (gold foil) experiment

Experiment that revealed a tiny, dense, positively charged nucleus within the atom; showed atoms are mostly empty space.

Alpha particle

A helium nucleus (He2+) emitted by radioactive substances; used in Rutherford’s experiments.

Beta ray

A fast-moving electron emitted by the nucleus; carries a negative charge.

Gamma ray

High-energy, uncharged electromagnetic radiation emitted by nuclei.

Atomic weight/Atomic mass

Weighted average mass of an element’s naturally occurring isotopes, expressed in atomic mass units.

Atomic mass unit (amu)

1/12 the mass of a carbon-12 atom; a convenient unit for quantifying atomic-scale masses.

Angstrom (Å)

A unit of length equal to 10^-10 meters; commonly used for atomic-scale distances; 1 Å ≈ 0.1 nm; being phased out in favor of picometers in many texts.

Picometer (pm)

A unit of length equal to 10^-12 meters; widely used for interatomic distances.

Cubic centimeter (cm^3)** / milliliter (mL)

1 cm^3 equals 1 mL; a convenient volume unit in chemistry.

Inch to centimeter conversion

1 inch = 2.54 cm; for volume, cube the conversion (in^3 to cm^3) to convert dimensions cubed.

Nucleus vs. electron cloud

Mass is concentrated in the tiny nucleus (protons and neutrons); electrons occupy a surrounding cloud, making most of the atom’s volume empty space.

Isotope notation

Symbol notation with mass number A on the top-left, atomic number Z on the bottom-left, the element symbol in the middle, and charge on the top-right.

Oxygen (O)**

Element with atomic number 8; neutral oxygen typically has 8 protons and 8 electrons (example isotope: oxygen-16 has 8 neutrons).

Hydrogen isotopes

Protium (1H): 1 proton, 0 neutrons; Deuterium (2H): 1 proton, 1 neutron; Tritium (3H): 1 proton, 2 neutrons.

Weighted average (isotope masses)

Atomic weights are weighted averages of isotope masses based on natural abundances.