Nuclear Radiation & Stability Lecture

Vocabulary flashcards summarizing the key nuclear chemistry concepts—types of radiation, particle definitions, and stability rules—presented in the lecture.

Positron

The positively-charged antiparticle of an electron mentioned in lecture as having no mass and symbolized 0⁺₁ e.

Antiparticle

A subatomic particle that has the same mass but opposite charge (or quantum numbers) to its corresponding particle; example: positron is the antiparticle of the electron.

Proton

Positively charged nuclear particle with mass ≈1 amu; its count equals the atomic number (Z).

Neutron

Neutral nuclear particle with mass ≈1 amu; helps stabilize the nucleus by offsetting proton–proton repulsion.

Atomic Number (Z)

The number of protons in a nucleus; determines the chemical identity of an element.

Mass Number (A)

The total number of protons plus neutrons in the nucleus of an atom.

Beta Particle (β⁻)

A high-speed electron (0⁻₁ e) emitted during β⁻ decay.

Beta Decay (β⁻)

Radioactive process where a neutron splits into a proton and an electron, keeping A constant while Z increases by 1.

Positron Emission (β⁺ decay)

Process where a proton transforms into a neutron and emits a positron (0⁺₁ e); A stays constant, Z decreases by 1.

Electron Capture

Nuclear reaction in which the nucleus draws in one of its inner electrons; the electron combines with a proton to form a neutron, decreasing Z by 1 while A stays the same.

Alpha Decay

Emission of an alpha particle (⁴₂He nucleus); typically occurs in very heavy nuclei (Z > 83).

Gamma Radiation (γ)

High-energy photons emitted from an excited nucleus, often following α or β decay, without changing A or Z.

N/Z Ratio

The ratio of neutrons (N) to protons (Z); a key indicator of nuclear stability.

Light Elements (Z < 20)

Elements whose stable isotopes generally have N ≈ Z (N/Z about 1).

Heavy Elements (Z > 20)

Elements that require extra neutrons for stability, giving N/Z ratios greater than 1.

Valley of Stability

The band on an N vs. Z plot where stable nuclei reside; nuclei outside this valley are radioactive.

Stable Nucleus

A nucleus that lies within the Valley of Stability and does not spontaneously undergo radioactive decay.

Unstable Nucleus

A nucleus located outside the Valley of Stability; tends to decay to reach a more stable state.

Too Many Neutrons (N≫Z)

Condition that often drives β⁻ decay to convert neutrons into protons and lower the N/Z ratio.

Too Few Neutrons (N≪Z)

Condition that promotes positron emission or electron capture to convert protons into neutrons and raise the N/Z ratio.

Very Heavy Nuclei (Z > 83)

Nuclei so massive that they frequently relieve instability by emitting α particles.

Magic Numbers

Specific proton or neutron counts that confer extra nuclear stability (topic previewed for next lecture).