CP6- RadioActivity Flashcards
Atomic Models
An atom has a small, positively-charged nucleus surrounded by orbiting negatively-charged electrons(in a shell).
Rutherford suggested that atoms were mostly empty space. with most of their mass in a tiny central nucleus with a positive charge and electrons moving around the nucleus.
Inside Atoms
Electron Mass: 1/1835
Isotopes- Atoms of a single element that have different numbers of neutrons(different mass numbers).
Electrons and Orbits
If an atom absorbs energy, an electron can move to a higher electron shell(orbit). When an electron returns to a lower orbit the atom emits energy as visible light (EM radiation). Electrons can make all these different orbit changes. Each different change produces a different wavelength of light.
Emission spectrum- A set of wavelengths of light showing which wavelengths have been given out by a substance. They are different for each element
Ionisation
Sometimes an atom gains so much energy that 1 or more electrons can escape from the atom.
An atom that has lost or gained electrons is called an ion. Radiation that causes electrons to escape is ionising radiation.
If an atom loses electron- positive ion, gains electron-negative ion
Background Radiation
Background Radiation- We are constantly being exposed to ionising radiation at a low level, from space and from naturally radioactive substances in the environment.
Cosmic Rays are a form of radiation. They are high energy charged particles from the sun.
Radiation can be measured using photographic film or a Geiger-muller tube
Types of Radiation
The nucleus of a radioactive substance is unstable, which means it can easily change or decay. When decay occurs, radiation is emitted which causes the nucleus to lose energy and become more stable
Alpha Particles contain 2 protons and neutrons like the nucleus of a helium atom. They have a relative mass of 4 and no electrons.
Beta Particles are high-energy high-speed electrons. They have a relative mass of 1/1835 and a charge of -1.
Types of Radiation Cont.
Positrons are high energy high speed particles with same mass of electrons but charge of 1+.
Gamma Rays are high frequency EM waves. No electric charge
Strength of Radiation:
Alpha- Travel few cm in air/Very ionising/stopped by sheet of paper
Beta- Travel few m in air/Moderately ionising/Stopped by 3mm thick aluminum
Gamma-Travel few km in air/Weakly ionising/Stopped by lead few cm thick
Half-Life
Halflife- Time taken for half the unstable nuclei in a sample of radioactive isotope to decay
- Activity of any radioactive substance is number of nuclear decays per second and is measured in Bequerels (bq).
- Half life of an isotope measures how long it takes for activity to halve.
Dangers of Radioactivity
A large amount of ionising radiation can cause tissue damage such as redenned skin.
Small amounts of ionising radiation over long periods of time can cause mutations in cells and may cause cancer.
Irradiated- When someone is exposed to alpha,beta or gamma radiation from radioactive materials
Contaminated- When someone gets radioactive material on skin or insidebody.
