atomic structure& radiation

• How does alpha decay alter the mass number of the parent nucleus?

  decreases by 4
• How does alpha decay alter the atomic number of the parent nucleus?

  decreases by 2
• How does beta decay alter the mass number of the parent nucleus?

  stays the same
• How does beta decay alter the atomic number of the parent nucleus?

  increases by 1
• which subatomic particle isn't in the nucleus?

  electrons
• What did Rutherford's experiment reveal?

  Atoms are mostly made up of empty space and have a small central area of positive charge.
• Who discovered that electrons are located in energy levels?

  neils bohr
• Isotope

  An element with the same number of protons but a different number of neutrons. They have the same atomic number, but different mass numbers.
• Some isotopes are unstable and as a result decay and give out radiation.
• Ionising radiation

  Radiation that can knock electrons off atoms. Just how ionising this radiation is depends on how readily (easily) it can do that.
• Types of radiation

  • Alpha
  • Beta
  • Gamma
• Alpha radiation

  • An alpha particle emitted from the nucleus of a radioactive nuclei. An alpha particle is made from two protons and two neutrons.
  • Alpha particles can't travel far in air and are the least penetrating- they are stopped by skin of a sheet of paper. However Alpha particles are the most ionizing – (they can knock electrons off other atoms really easily and if they were inside your body would be dangerous).
• Beta radiation

  • A fast moving electron that can be stopped by a piece of aluminium. Beta radiation is emitted by an atom when a neutron splits into a proton and an electron.
  • Beta can travel a few meters in air and is stopped by 5mm of aluminium and is only slightly ionising.
• Gamma radiation

  • A wave of radiation and is the most penetrating – stopped (or slowed down) by thick lead and concrete. Gamma is the least ionising of the three types and will travel very far in air.
• Alpha radiation inside the body

  More dangerous as it is highly ionising and able to cause a lot of damage
• Alpha radiation outside the body

  Less dangerous because it cannot penetrate the skin
• Beta radiation inside the body

  Less dangerous as some of the radiation is able to escape
• Beta radiation outside the body

  More dangerous as it can penetrate the skin
• Gamma radiation inside the body

  Least dangerous as most will pass out and it is the least ionising
• Gamma radiation outside the body

  More dangerous as it can penetrate the skin
• Half-life

  The time taken for the number of radioactive nuclei in an isotope to halve.
• Radioactivity is a random process- you will not known which nuclei will decay.
• Radioactive decay

  Measured in Becquerels (Bq). 1 Bq is one decay per second.
• Irradiation

  1. Materials are deliberately placed near a radioactive source. Often the source is kept in a lead lined box to avoid irradiation of unwanted objects.

  2. People who work with radioactive sources will sometimes stand behind a lead barrier, be in a different room or use a remote controlled arm when handling the radioactive substances.
• Contamination

  When unwanted radioactive atoms get onto an object, it is possible for the radioactive particles to get inside the body. Protective clothing should be worn when handling radioactive material.
• There is no change to the nucleus when a radioactive source emits gamma radiation. It is the nucleus getting rid of excess energy.
• Alpha decay

  An Alpha particle is made of two protons and two neutrons. The atomic number goes down by two and its mass number decreases by four.
• Beta decay

  A neutron turns into a proton and releases a fast moving electron. The mass of the nucleus does not change but the number of protons increases by one.