Introduction to Atoms and Radioisotopes in CHEM 150

Protons

Positive charge particle with an Atomic Mass Unit of 1 located in the nucleus of the atom. The atomic number identifies the element.

Electrons

Negative particle with an Atomic Mass Unit of 0 that surrounds the nucleus. This particle determines the charge on the atoms. The Atomic Number - Charge = Number of Electrons.

Neutrons

Neutral charge particle in the nucleus of the atom with an Atomic Mass Unit of 1. Mass Number - Atomic Number = number of ______. The number of _______ determines the isotope of the element.

Nucleus

The center of the atom containing the protons and neutrons which makes up 99.999% of the mass of the atom.

Electron Orbitals

The space electrons are found circulating around the nucleus of the atom and accounts for 99.999% of the atom's volume.

Atomic Number

The whole number on the periodic table identifying the number of protons in the elements.

Mass Number

The number of protons and neutrons in the nucleus of the element.

Atomic Mass

The relative mass of an atom/element; the mass for one mole of the atom/element.

Charge

The number of protons minus the number of electrons gives the charge. Atoms with charge are called ions.

Ion

Atoms or molecules with a charge.

Isotope

Determined by the number of neutrons in the element. Some are unstable causing the element to break apart creating a nuclear reaction.

Half-life

The amount of time it takes for a radioisotope to decay to half its original mass.

Radioactive Particles

Alpha (α) +2, Beta (β) -1, Gama (γ) 0, Positron (p) +1, Neutron (n) 0.

Balancing Nuclear Equations

1. The mass number on the reactant side must equal the total mass balance on the product side.

2. The atomic number on the reactant side must equal the total atomic number on the product side.

Determining Missing Particles in a Nuclear Reaction

1. Balance the equation to identify the mass number and atomic number of the missing particle.

2. From the atomic and mass number, determine the missing element or emission particle.

Half-life

The time it takes for half of the radioisotopes to react.

Radioisotope

An isotope that exhibits radioactivity.

Example of half-life calculation

A radioisotope has a half-life of 5 days. In 15 days, there are 3 half-lives.

Grams left after half-lives

If 60 g of a radioisotope with a half-life of 20 days has reacted for 3 half-lives, it can be calculated as 60/2 = 30, 30/2 = 15, 15/2 = 7.5.