Radioactivity

• • [Isotopes] are atoms with the same number of Protons, and a DIFFERENT number of Neutrons

  So, they have the same ATOMIC Numbers, but different MASS Numbers

  A) Different

  B) Same

  
• Isotope Decay:

  • Usually, each Element only has 1 or 2, STABLE ISOTOPES. The other Isotopes tend to be RADIOACTIVE

  ---> This is because the Nucleus is Unstable, so it DECAYS (breaks down), and Emits Radiation

  A) -

  
• Electron ENERGY LEVELS in Atoms:

  • Every Atom contains Electron Shells, which we call ENERGY LEVELS
  • The FURTHER away the Shell is from the Nucleus, the HIGHER the Energy Level will be

  If they gain enough ENERGY, Electrons can 'Jump Up' an Energy Level (shell). The Electron has now become EXCITED

  ---> the energy for this, comes from ELECTROMAGNETIC RADIATION

  A) increasing

  B) Energy

  C) excited

  D) electromagnetic radiation

  
• IONISATION:

  • Sometimes, one of the Outermost Electrons can absorb SO MUCH ENERGY, that it's able to completely Leave the Atom

  --> This leaves the Atom with more PROTONS than Electrons, so its left with a Positive Charge, making it a [POSITIVE ION]

  A) ionising

  
• When we say that a material is [Radioactive], we mean that it consists of unstable ISOTOPES that can Decay

  A) -

  
• ALPHA Particles (α)

  2 Protons, 2 Neutrons

  • Alpha Particles are HELIUM Nuclei. They have an overall charge of 2+
  • Alpha Particles are relatively LARGE, so they are easily stopped by Collisions with other Molecules

  ---> (meaning they can't penetrate very far into other materials)

  • STOPPED BY :: [Absorbed] by a Single Sheet of Paper

  A) Ionising

  B) knock electrons

  C) collide

  D) penetrate

  
• BETA Particles (β)

  An Electron

  • They have a Charge of 1-, and pretty much NO MASS
  • They are Electrons, which have been Emitted from the Nucleus of an Atom, when a Neutron turns into a Proton AND, an Electron (which is emitted at HIGH Speed)

  ---> STOPPED BY :: 5mm of Aluminium

  A) Moderately

  B) Moderately

  C) Several

  D) Aluminium

  
• GAMMA Rays (γ)

  Energy in the form of Electromagnetic WAVES (Emitted AFTER α or β Radiation)

  • They have NO MASS or CHARGE, so they can Pass Through Materials, without colliding into any atoms, making them WEAKLY Ionising

  ---> STOPPED BY :: Thick Sheets of Lead, OR Multiple METRES of Concrete

  A) weakly

  B) far

  C) long

  D) lead

  E) metres

  F) concrete

  
• [Nuclear Decay Equations]

  ALPHA Decay

  A) 4

  B) 2

  C) 234

  D) 90

  E) 4

  F) 2

  G) Different

  
• [Nuclear Decay Equations]

  BETA Decay

  • The Atomic Number INCREASES by 1, since a Proton has been GAINED

  A) Gained

  B) INCREASE

  C) 14

  D) 7

  E) 0

  F) -1

  
• [Nuclear Decay Equations]

  GAMMA Radiation

  • A Gamma Ray has No MASS, and No CHARGE, so the Mass Number and Atomic Number stay the SAME

  A) 234

  B) 90

  C) gamma

  
• [Nuclear Decay Equations]

  NEUTRON Emission

  A) Subtract

  B) 8

  C) 4

  D) 1

  E) 0

  
• [Activity] is the OVERALL Rate of Decay, of ALL Isotopes in our sample

  • It is measured in Becquerels where: 1 Bq = 1 Decay per Second
  • So, if a Sample had an activity of 600 Becquerels, then there are 600 Isotopes decaying EACH SECOND in that Sample

  A) -

  
• There are TWO definitions for Half Life:

  [Half-Life] is the Time Taken for the number of Radioactive NUCLEI in a sample to HALVE

  OR

  [Half-Life] is the Time Taken for the ACTIVITY (or Count Rate) in a sample, to fall by HALF

  A) -

  
• Half Life Exam Question:

  A) 24

  B) 120

  C) 3

  D) 375000

  
• • [Background Radiation] is LOW LEVEL, Natural Nuclear Radiation that is always present AROUND US

  This comes from:

  • Radiation of Sun Rays, from Space
  • Living Things
  • Human Activity (like Nuclear Power Stations / Nuclear Waste)

  A) -