What is an isotope? Agenda for Tuesday Feb 8th Percent composition Radiation

Radioactivity Radioactivity: the process of an unstable nucleus emitting one or more particles in the form of electromagnetic radiation.

History of Radiation Henri Becquerel Discovered radioactivity when using photographic paper. He was testing florescent substances.

History of Radiation Marie and Pierre Curie Used Becquerel’s findings in their research. This led to the discovery of three radioactive elements.

Characteristics of Radioactive Substances Can alter photographic paper Produces florescence in some substances Electrical charges can be detected in the surrounding air May damage cells in living organisms

Three different types of radioactive particles: Alpha: Weakest type of radiation. Has a positive charge (+2) An alpha particle is a helium nucleus (two protons and two neutrons) Can be stopped by a thin piece of paper or a layer of dead skin

Types of particles Beta Has a negative charge. (-1) Beta particles are electrons produced when a neutron decays. Can be stopped by 3mm of aluminum foil or 10 mm of wood.

Types of particles Gamma rays Strongest type of radiation Gamma rays are pure energy not physical particles. They have no charge Several cm of lead are needed to stop gamma rays

Nuclear Decay Series: Alpha decay An atom releases an alpha particle, which is the same as a helium nucleus. The new element has two less protons and neutrons than the original element.

Nuclear Decay Beta decay An atom releases Beta particles, or an electron. Think of a neutron as a proton and electron together. When the electron leaves the proton is left behind. This produces a new element with one more proton.

Nuclear Decay Gamma Decay The nucleus is not changed, so the element remains the same.

Equipment used to detect radiation: Photographic paper Each type of decay leaves a “finger print” on the paper. Geiger counter A gas filled tube. When radioactive rays enter the tube it causes an electrical current. The more particles the more current.

Nuclear Radiation Today You are exposed to radiation every day. Background radiation – radiation that naturally occurs from cosmic rays and radioactive isotopes in the soil, air sun, heat, rocks and plants Living things are adapted to survive low levels of radiation, but more than low levels can be a health hazard.

Radon Gas Colorless, odorless gas produced by the radioactive decay of uranium-238 Radon gas emits alpha and beta particles and gamma rays Has been linked to lung cancer

Measuring Radiation Geiger Counter – tool used to measure the amount of radiation in an area rems or mrems - unit used to measure the amount of radiation absorbed by the human body

Radiation Can Be Useful Examples: Smoke detectors Detection of diseases Treatment for cancer

What is radiation? Agenda for Wednesday Feb 9th 1. Alpha, Beta, and gamma decay

Alpha, Beta, and Gamma Decay Nuclear Reactions Alpha, Beta, and Gamma Decay

CS 4.2 State what is meant by alpha, beta and gamma decay of radionuclides. CS 4.3 Identify the processes occurring in nuclear reactions written in symbolic form.

The Atom The atom consists of two parts: 1. The nucleus which contains: protons neutrons 2. Orbiting electrons.

The Atom All matter is made up of elements (e.g. carbon, hydrogen, etc.). The smallest part of an element is called an atom. Atom of different elements contain different numbers of protons. The mass of an atom is almost entirely due to the number of protons and neutrons.

X A Z Mass number = number of protons + number of neutrons Element symbol Z Atomic number = number of protons

X A Z A = number of protons + number of neutrons Z = number of protons A – Z = number of neutrons Number of neutrons = Mass Number – Atomic Number

U U 235 92 238 92 There are many types of uranium: A Z Number of protons Number of neutrons A Z Number of protons Number of neutrons

U U 235 92 238 92 There are many types of uranium: A 235 Z 92 Number of protons Number of neutrons 143 A 238 Z 92 Number of protons Number of neutrons 146 Isotopes of any particular element contain the same number of protons, but different numbers of neutrons.

Most of the isotopes which occur naturally are stable. A few naturally occurring isotopes and all of the man-made isotopes are unstable. Unstable isotopes can become stable by releasing different types of particles. This process is called radioactive decay and the elements which undergo this process are called radioisotopes/radionuclides.

Radioactive Decay Radioactive decay results in the emission of either: an alpha particle (a), a beta particle (b), or a gamma ray(g).

Alpha Decay An alpha particle is identical to that of a helium nucleus. It contains two protons and two neutrons.

X Y + He Alpha Decay A Z A - 4 Z - 2 4 2 unstable atom alpha particle more stable atom

Alpha Decay Rn 222 86 He 4 2 Ra 226 88

Alpha Decay X A Z Y A - 4 Z - 2 + He 4 2 Ra 226 88 Rn 222 86 + He 4 2

Alpha Decay Rn 222 86 + Y A Z He 4 2 Rn 222 86 He 4 2 + Po 218 84

Alpha Decay X A Z + Th 230 90 He 4 2 He 4 2 U 234 92 + Th 230 90

Alpha Decay Th 230 90 + Y A Z He 4 2 He 4 2 + Ra 226 88 Th 230 90

Alpha Decay X A Z + Pb 214 82 He 4 2 He 4 2 + Pb 214 82 Po 218 84

Beta Decay A beta particle is a fast moving electron which is emitted from the nucleus of an atom undergoing radioactive decay. Beta decay occurs when a neutron changes into a proton and an electron.

Beta Decay As a result of beta decay, the nucleus has one less neutron, but one extra proton. The atomic number, Z, increases by 1 and the mass number, A, stays the same.

Beta Decay b -1 At 218 85 Po 218 84

Beta Decay X A Z Y Z + 1 + b -1 Po 218 84 Rn 85 + b -1

Beta Decay Th 234 90 Y A Z + b -1 Th 234 90 Pa 91 + b -1

Beta Decay X A Z Pb 210 82 + b -1 Tl 210 81 Pb 82 + b -1

Beta Decay Bi 210 83 Y A Z + b -1 Bi 210 83 Po 84 + b -1

Beta Decay X A Z Bi 214 83 + b -1 Pb 214 82 Bi 83 + b -1

Gamma Decay Gamma rays are not charged particles like a and b particles. Gamma rays are electromagnetic radiation with high frequency. When atoms decay by emitting a or b particles to form a new atom, the nuclei of the new atom formed may still have too much energy to be completely stable. This excess energy is emitted as gamma rays (gamma ray photons have energies of ~ 1 x 10-12 J).

Gamma Ray A gamma is a high energy light particle. It is NOT visible by your naked eye because it is not in the visible part of the EM spectrum.

Radioactive Dangers Energy Alpha Low Beta Medium Gamma High Paper Wood September 19, 2018 Radioactive Dangers Paper Wood Concrete Alpha Beta Gamma Energy Low Medium High A Small Dose of Toxicology - Overview

Alpha Particles Transfer energy in very short distances (10 cm in air) September 19, 2018 Alpha Particles Transfer energy in very short distances (10 cm in air) Shielded by paper or layer of skin Primary hazard from internal exposure Alpha emitters can accumulate in tissue (bone, kidney, liver, lung, spleen) causing local damage A Small Dose of Toxicology - Overview

Beta Particles Emitted with various kinetic energies September 19, 2018 Beta Particles Emitted with various kinetic energies Shielded by wood, body penetration 0.2 to 1.3 cm depending on energy Can cause skin burns or be an internal hazard of ingested A Small Dose of Toxicology - Overview

Gamma-rays Very high energy September 19, 2018 Gamma-rays Very high energy Highly penetrating – extensive shielding required Serious external radiation hazard A Small Dose of Toxicology - Overview

Types of Radiation Practice