Nuclear Chemistry Terms

Half-Life

Time required for half of a radioactive sample to decay.

Isotope

Atoms of the same element with different numbers of neutrons.

Radioactivity

Spontaneous emission of particles or energy from an unstable nucleus.

Neutrons

Neutral particles in the nucleus, important for stability.

Transmutation

Process of one element changing into another.

Iodine-131; Carbon-14; Cobalt-60

Examples of radioisotopes used in medicine and dating.

Nuclear Reactions

Reactions that involve changes in an atom’s nucleus.

Nucleus

Dense center of an atom containing protons and neutrons.

Radioisotope

A radioactive form of an element.

Mass Number

Sums of protons and neutrons in an atom.

Radiation

Energy or particles emitted during radioactive decay.

Fission

Splitting of a large nucleus into smaller ones (used in nuclear power)

Fusion

Combining small nuclei to form a larger one (powers the sun)

Proton

Positively charged particles in the nucleus

Stable

A nucleus that does not undergo radioactive decay easily

Chemical reactions vs. Nuclear reactions

Chemical changes involve electrons; nuclear changes involve the nucleus

Band of stability

Region of the graph where stable nuclei exist

Transuranium elements

Elements with atomic numbers greater than 92

Particle accelerators

Devices used to produce high-speed particles

Chain Reaction

A self- sustaining fission reaction

Alpha (α)

• symbol: α or 4/2 He

• Charge: +2

• Mass: Heavy

• Penetration: Low (stopped by paper)

• Effect: Mass # decrease by 4, atomic number decrease by 2

Beta (β)

• Symbol: β

• Charge: -1

• Mass: very small

• Penetration: Moderate (stopped by foil)

• Effect: Neutron converts into a proton/ increases atomic number by one

Gamma (γ)

• Symbol: γ/gamma

• Charge: 0

• Mass: 0

• Penetration: Very high (needs lead to stop)

• Often emitted with alpha or beta particles

Penetrating power of radiation in order of strength

1. Gamma

2. Beta

3. Alpha

Half life

• After on half life, 50% remains

• use exponential decay to solve for remaining amounts

Stability of Uranium

some isotopes are unstable and undergo radioactive decay

Reverse Half-life

• if 25% remains→ 2 half ives

• Total time= 2× 12.3; Total time= 24.6 years