Nuclear Chemistry

Atom

smallest unit of an element that retains its identity in a chemical reaction and all the characteristics of that element

Neutron (n)

Neutral Charge

Found in nucleus

Proton (p+)

atomic number

positive charge

found in nucleus

electron (e-)

negative charge

found outside of nucleus

same number as protons in neutral atom

Mass number

total number of protons and neutrons in an atom

Atomic number

the total number of protons in an atom

What makes one element different from another?

Protons

Isotopes

atoms of the same element that have equal protons but different number of neutrons

Atomic mass

the weighted average of all isotopes in a naturally occurring sample of the element

Stable Isotopes

isotopes that are non-radioactive forms of atoms

*typically the most stable form of an element is the most common in nature

Unstable Isotopes

isotopes of an element that emit ionizing radiation are called radioactive

*also called radioisotopes

What does radioactive mean?

an isotope is "radioactive" if its nucleus had a probability of spontaneously changing over time

Radioactive

a spontaneous process of an unstable atom transitioning into a more stable form by emitting matter or energy

Radiation

emitting matter and energy

Elements are unstable because:

*The nucleus is too large - too many protons and neutrons

*an unstable ratio of protons to neutrons

*the larger it is the more unstable it is

When unstable isotopes go through radioactive decay....

*they become "more stable" when changes occur in their nuclei

*during radioactive decay, a "parent" isotope transforms into a "daughter" isotope and releases ionizing radiation in the form of matter

Radioactive Decay.....

*if the product (or daughter isotope) of a nuclear reaction is unstable, it will continue to decay

*process continues until a stable isotope if formed

*these stable isotopes are not radioactive

*heavy radioactive elements ultimately decay into lead

Beta Decay

process used by unstable atoms to become more stable

Beta Minus

*decay happens when a neutron becomes a proton and electron

*electron is emitted

*the atomic mass is unchanged and the atomic number increases by 1

Gamma Decay

*after alpha or beta decay they are left excited

*the nucleus gives off gamma rays

*gamma rays have no mass and no electrical charge

*so... does not alter the atomic number or mass number of the atom

Ionizing Radiation

a type of energy released by atoms in the form of waves (gamma) or particles (alpha or beta)

*can travel unseen and pass through materials. In the process probably removing electrons from atoms or molecules of material

Health Risks

direct - ionizing radiation directly hits DNA causing damage

indirect - radiation may be absorbed in the water of an organism causing excitation and ionizing of the water (free radicals). Radicals then react with DNA molecules to cause structural damage.

Health Effects

*skin burn or tissue damage

*acute radiation syndrome - very high levels of radiation exposure delivered over a short period of time - illness that last hours to days and could result in death

*low doses can increase the risk of long term effects

Good Effects

radiation is a common and valuable tool in medicine, research, and industry

*kills harmful bacteria in food to extend shelf life

*smoke detectors

*nuclear power

Alpha Particles

*highest ionization

*very energetic, but heavy

*cannot penetrate the outer layer of skin

*can cause damage in your body

Alpha Therapy

*targets and kills cancer cells

*short range

Marie Currie

*founding mother of nuclear chemistry

*helped with radiation

*won 2 nobel peace prizes

Beta Particles

*Fast moving, lighter particles

*can penetrate outer layers of skin

*cause ions in the body

*does less damage to living tissue in DNA

Gamma Particles

*Gamma rays are pure energy waves

*can pass completely through human body

*could cause ionizations that damage tissue and DNA

*lower concentration of ions in their path to cause DNA damage

Half-Life

*Radioactive decay depends of chance

*the time it takes for half of the original sample of radioactive material to go through radioactive decay

Carbon Dating

*Carbon - 14 is used for carbon dating

*Used to date fossils