Lesson #3 - Isotopes, Radioisotopes, and Atomic Mass

Isotope

a form of an element that has the same number of protons
(same atomic number), but different number of neutrons (different atomic mass)

isotopic abundance

the percentage of a given isotope in a sample of an element

mass spectrum

a measuring instrument used to determine the mass and abundance of isotopes

radioactive decay

the spontaneous disintegration (breaking
apart) of unstable isotopes

nuclear radiation

energy, or very small particles, emitted from the nucleus of a radioisotope as it decays

alpha particle

a product of nuclear decay, emitted by certain radioisotopes; a positively charged particle with the same structure as the nucleus of a helium atom (2 protons, 2 neutrons - but has a change of +2). These particles can be blocked by paper

beta particle

a product of nuclear decay, emitted by certain radioisotopes; a negatively charged particle,
identical to an electron. This particle can pass through paper, but not through aluminum

gamma ray

a form of high energy electromagnetic
radiation, emitted by certain radioisotopes. These rays have no mass and travel at the speed of light
(3.00x108 m/s). They can penetrate most substances, but are blocked by lead

Radioisotopes

Isotopes that decay and produce nuclear radiation (they
produce two or more smaller nuclei and radiation). All isotopes of uranium are radioisotopes (there are no
stable uranium isotopes). All radioisotopes are radioactive

average atomic mass

Atomic mass (also known as average atomic mass) - the
average of the masses of all of the naturally occurring
isotopes of an element (taking into account their
abundances)

Calculating average atomic mass

Average atomic mass = mass of isotope 1 x isotopic
abundance of isotope 1 + mass of isotope 2 x isotopic
abundance of isotope 2...