Isotopes, Radioisotopes, and Atomic Mass

Vocabulary flashcards covering isotopes, isotopic abundance, mass spectrometry, atomic mass, radioisotopes, and carbon-14 dating.

Isotope

An atom of the same element that has the same number of protons but a different number of neutrons, resulting in different mass numbers.

Mass number (A)

The total number of protons and neutrons in the nucleus; for example, carbon-12 has A = 12.

Atomic number (Z)

The number of protons in the nucleus; defines the element.

Atomic mass

The weighted average mass of an element’s atoms as they occur in nature, measured in atomic mass units (amu).

Isotopic abundance

The fraction or percentage of a specific isotope in nature.

Mass spectrometer

An instrument that ionizes a sample and separates ions by mass to identify isotopes and their abundances.

Weighted average atomic mass

The sum of (isotope mass × isotopic abundance) for all isotopes of an element, giving the element’s atomic mass.

Atomic mass unit (amu)

A relative unit of mass defined as 1/12 the mass of carbon-12; used to express atomic and molecular masses.

Mole

A unit representing 6.022×10^23 particles, used to relate grams to the number of atoms or molecules.

Radioisotope

An isotope that is unstable and decays, emitting radiation.

Nuclear radiation

Energy or particles emitted from the nucleus during radioactive decay.

Alpha particle

A helium-4 nucleus (2 protons, 2 neutrons); low energy and generally stopped by paper.

Beta particle

A high-energy electron emitted during decay; more penetrating and can be stopped by aluminum.

Gamma ray

High-energy electromagnetic radiation emitted during decay; highly penetrating and requires dense shielding like lead.

Half-life

The time required for half of a radioactive substance to decay.

Carbon-14 dating

A dating method that uses the decay of carbon-14 to estimate the age of formerly living material.

Decay

The process by which a radioactive nucleus breaks down to a different nucleus, releasing radiation.

Carbon-14 beta decay to nitrogen-14

In beta decay, a neutron in carbon-14 converts to a proton and an electron, turning C-14 into N-14.

Proton

Positively charged subatomic particle in the nucleus; number of protons defines the element.

Neutron

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