Atoms and Isotopes What are atoms, isotopes, and radioactive decay?

The Harnessed Atom 2 Atoms and Isotopes Atoms and Subatomic Particles Atoms are the smallest unit of a chemical element that has all the chemical properties of that element. Atoms are the smallest unit of a chemical element that has all the chemical properties of that element. Made up of: Made up of: Protons– positive charge Protons– positive charge Neutrons—no charge Neutrons—no charge Electrons—negative charge Electrons—negative charge

The Harnessed Atom 3 Atoms and Isotopes The Periodic Table of the Elements

The Harnessed Atom 4 Atoms and Isotopes Reading Atomic Notations Z is the atomic (proton) number Z is the atomic (proton) number N is the neutron number N is the neutron number A is the mass number (N+Z) A is the mass number (N+Z) X is the chemical element symbol X is the chemical element symbol

The Harnessed Atom 5 Atoms and Isotopes Isotopes Atoms of one element may have different number of neutrons: the different possible versions of each element are called isotopes. Atoms of one element may have different number of neutrons: the different possible versions of each element are called isotopes. Isotopes of one element all have the same number of protons (atomic number, Z) but different numbers of neutrons (thus different atomic weights, A). Isotopes of one element all have the same number of protons (atomic number, Z) but different numbers of neutrons (thus different atomic weights, A). Every element has several isotopes Every element has several isotopes All isotopes are shown on the chart of the nuclides. All isotopes are shown on the chart of the nuclides.

The Harnessed Atom 6 Atoms and Isotopes Radioactive Decay Unstable atoms will spontaneously transform until they reach a stable configuration. Unstable atoms will spontaneously transform until they reach a stable configuration. These transformations are accompanied by releases of energy. These transformations are accompanied by releases of energy.

The Harnessed Atom 7 Atoms and Isotopes Radioactive Decay This energy, given off in waves from an atom, is known as radiation. This energy, given off in waves from an atom, is known as radiation. Substances that give off radiation are called radioactive. Substances that give off radiation are called radioactive. The process of isotopes emitting particles and energy to become more stable is called radioactive decay. The process of isotopes emitting particles and energy to become more stable is called radioactive decay.

The Harnessed Atom 8 Atoms and Isotopes Radioactive Decay Main types of radioactive decay: Main types of radioactive decay: Alpha emission Alpha emission Beta emission Beta emission Positron emission Positron emission Gamma emission Gamma emission

The Harnessed Atom 9 Atoms and Isotopes Radioactive Decay Alpha emission ( α ) Nucleus emits an alpha particle—two protons and two neutrons Equivalent to a helium nucleus (He). Alpha Decay Animation

The Harnessed Atom 10 Atoms and Isotopes Radioactive Decay Beta Emission ( β ) Nucleus emits an electron, and a neutron is converted to a proton. Nucleus emits an electron, and a neutron is converted to a proton. Beta Decay Animations:

The Harnessed Atom 11 Atoms and Isotopes Radioactive Decay Positron Emission Nucleus emits a positron (identical to an electron in mass, but has a positive charge) Nucleus emits a positron (identical to an electron in mass, but has a positive charge) Positron is formed when a proton converts to a neutron. Positron is formed when a proton converts to a neutron.

The Harnessed Atom 12 Atoms and Isotopes Radioactive Decay Gamma emission ( γ ) Nuclei seeking lower energy states emit electromagnetic radiation, which is in the gamma ray region of the electromagnetic spectrum. Nuclei seeking lower energy states emit electromagnetic radiation, which is in the gamma ray region of the electromagnetic spectrum. Rays are emitted in conjunction with another type of decay (alpha or beta). Rays are emitted in conjunction with another type of decay (alpha or beta). Gamma Decay Additional animations:

The Harnessed Atom 13 Atoms and Isotopes Radioactive Decay Chains

The Harnessed Atom 14 Atoms and Isotopes Half Life The amount of time it takes for half of the atoms of a given isotope to decay to another form is known as its half-life. The amount of time it takes for half of the atoms of a given isotope to decay to another form is known as its half-life. The value can be from fractions of a second to billions of years. The value can be from fractions of a second to billions of years.

The Harnessed Atom 15 Atoms and Isotopes Half Life Half-life values are constant. Half-life values are constant. There is no way to speed up or slow down this natural process. There is no way to speed up or slow down this natural process. Cannot predict when a specific atom will decay. Cannot predict when a specific atom will decay. Can predict the number of atoms that will decay in a certain time period. Can predict the number of atoms that will decay in a certain time period.

The Harnessed Atom 16 Atoms and Isotopes Half Life of Uranium-235