Chemistry Unit 1, Lesson 2: Isotopes, Radioisotope, and Average Atomic Mass

Isotopes

Atoms of the same element with different mass numbers.

Neutrons

Subatomic particles in the nucleus of an atom that have no charge.

Protons

Subatomic particles in the nucleus of an atom that have a positive charge.

Electrons

Subatomic particles that orbit the nucleus of an atom and have a negative charge.

Standard atomic notation

A way to represent isotopes using the element symbol and mass number.

Hyphen notation

A way to represent isotopes by writing the element name followed by the mass number, e.g., carbon-12 or C-12.

Relative atomic mass

The mass of an isotope determined relative to a C-12 atom.

Atomic mass unit (u)

A unit of mass equal to 1/12 the mass of a C-12 atom.

Average Atomic Mass

The weighted average of all isotopes of an element, calculated using % abundance and mass of each isotope.

Average Atomic Mass formula

[(mass 1)(%) + (mass 2)(%) + … ]/100 = AAM

Mass spectrograph

An instrument used to separate isotopes by mass.

Radioisotopes

Unstable isotopes that decay and emit radiation from the nucleus.

Uses of Radioisotopes

Includes radiation therapy for cancer, medical diagnostics, dating (C-14), and composition analysis.

Half-Life

The time it takes for half of the original radioactive substance to decay.

P=A(1/2)^t/h

P is product left over
A is amount started with
t is time spent
h is half life

Radiation emitted

The type of radiation released during the decay of a radioisotope.

Composition Analysis

A method using radioisotopes to analyze the composition of materials.

Abrasion studies

Research involving the use of radioisotopes to study wear in engines and tires.

C-14 dating

A method of determining the age of an object containing organic material by measuring the amount of C-14 it contains.