Atomic Structure and Isotopes - Vocabulary Flashcards

Vocabulary flashcards covering atomic structure, isotopes, masses, charges, and related concepts from the lecture notes.

Atom

Basic building block of matter composed of a nucleus (protons and neutrons) surrounded by an electron cloud; its composition and structure determine macroscopic properties.

Nucleus

Tiny, dense center of an atom containing protons and neutrons; accounts for virtually all the atom’s mass and is about 10^-14 m in size.

Electron cloud

Region around the nucleus where electrons move; makes up most of the atom’s volume and contributes negligibly to mass.

Macroscopic vs nanoscopic scale

Macroscopic scale is about 10^-3 m and larger; nanoscopic scale is about 10^-9 m or smaller, where atoms and chemistry operate.

Ångström (Å)

Unit of length equal to 10^-10 m; 1 Å = 100 pm; commonly used to express atomic-scale distances.

Proton

Positively charged subatomic particle in the nucleus; charge +1.602×10^-19 C; mass ≈ 1.6726×10^-27 kg.

Neutron

Electrically neutral subatomic particle in the nucleus; mass ≈ 1.6749×10^-27 kg; no electric charge.

Electron

Negatively charged subatomic particle in the electron cloud; charge -1.602×10^-19 C; mass ≈ 9.1094×10^-31 kg.

Coulomb’s law

Electrostatic force between charges: F = k Q1 Q2 / r^2; force binds electrons to protons and governs charge interactions.

Atomic number (Z)

Number of protons in the nucleus; determines the identity of the element.

Isotopes

Atoms of the same element (same Z) that have different numbers of neutrons and therefore different masses.

Mass number (A)

Total number of protons and neutrons in the nucleus; shown as a superscript in isotope notation.

Atomic symbol notation

Notation for isotopes such as 12C or 3H; sometimes the atomic number is omitted for common isotopes.

Atomic mass unit (amu)

1/12 the mass of carbon-12; 1 amu ≈ 1.66054×10^-27 kg; standard unit for atomic masses.

Isotopic abundance (natural abundance)

Fraction of each isotope found in nature; used to calculate average atomic mass.

Atomic weight (AW)

Weighted average mass of all naturally occurring isotopes of an element; appears in the periodic table.

Mass spectrometry

Technique to determine isotope masses and abundances by measuring how ions travel in a magnetic field.

Conservation of mass

In chemical reactions, nuclei remain unchanged; only electron clouds rearrange; total mass is conserved.

Hydrogen isotopes (protium, deuterium, tritium)

Protium (1H) is most abundant; deuterium (2H, D) has one neutron; tritium (3H, T) has two neutrons and is radioactive.