Nuclear Chemistry Study Guide: C19.1 & C19.3

Nucleus

The dense center of an atom, containing protons(+) and neutrons(neutral).

Proton

A subatomic particle with a positive charge(+1) and a mass of approximately 1 amu, found in the nucleus.

Neutron

A subatomic particle with no charge (0) and a mass of approximately 1 amu, found in the nucleus.

Electron

A subatomic particle with a negative charge(-1) and negligible mass, orbits the nucleus.

Atomic Number (Z)

The number of protons in an atom, defines the element.

Mass Number (A)

The total number of protons + neutrons in the nucleus.

Isotope

Atoms that have the same number of protons but different numbers of neutrons.

Unstable Atom

An atom with a nucleus that has too many or too few neutrons compared to protons, making it likely to decay.

Radiation

Particles and/or energy emitted by unstable nucleus to become more stable.

Neutron-to-Proton Ratio

The key factor that affects nuclear stability; too high or too low → unstable.

Alpha Decay

A nucleus emits an _______ (⁴₂He); atomic number decreases by 2, mass number decreases by 4.

Beta Decay

A neutron converts to a proton and emits a _______(⁰₋₁e); atomic number increases by 1, mass number stays the same.

Gamma Decay

Nucleus emits _________ (γ); energy is released, but no particles, no change in atomic or mass number.

Nuclear Process

A reaction that involves the nucleus (protons and neutrons), releasing much more energy than chemical reactions.

Fission

A large nucleus splits into smaller nuclei + energy + neutrons; fragments have fewer protons. Example: Uranium-235 → Barium + Krypton + 3 neutrons.

Fusion

Two small nuclei combine to form a larger nucleus + energy; resulting nucleus has more protons than either original. Example: Hydrogen isotopes → Helium.

Half-Life (t½)

The time it takes for half of a radioactive sample to decay; used to calculate remaining nucleus

Daughter Nucleus

The product of a radioactive decay reaction, usually more stable than the parent nucleus.

Kinetic Energy

Energy from moving particles released during decay (like alpha or beta particles).

Electromagnetic Energy

Energy released as gamma radiation (γ) during decay.

Absorption (Nuclear)

When a nucleus absorbs energy, which may trigger fission or fusion.

Particle Emission

Release of alpha, beta, or other particles from an unstable nucleus.

Nuclear Reactor

Device used for controlled fission to produce energy.

Nonionizing Radiation

Radiation that does not remove electrons from atoms; opposite of alpha, beta, gamma.

Nuclear Mass

Mass of the nucleus, slightly less than the sum of protons and neutrons due to mass defect.

Mass Defect

Difference between the nucleus’s mass and the sum of its protons + neutrons; mass lost → energy released.

Chemical Reaction Energy

Energy change in chemical reactions; much smaller than nuclear reactions.

Decay Chain

A series of radioactive decays where one unstable nucleus transforms into another unstable nucleus, and this continues until a stable nucleus is finally formed.

Chain Reaction

A self-sustaining series of reactions in fission or fusion where released neutrons trigger more reactions.