Particles

• What is the relative mass of a proton?

  1
• What is the relative mass of a neutron?

  1
• What is the relative mass of an electron?

  1/2000 or negligible
• What is the relative charge of a proton?

  +1
• What is the relative charge of a neutron?

  0
• What is the relative charge of an electron?

  • 1
• What is the overall charge of an atom?

  Neutral or zero
• What is the overall charge of a nucleus?

  Positive
• What is the approximate size of an atom?

  1 x 10^-10 m
• What is the approximate size of a nucleus?

  1 x 10^-15 m
• What is found between the nucleus and electrons?

  Empty space
• In A-Z nuclide notation, what does A represent?

  Nucleon number
• In A-Z nuclide notation, what does Z represent?

  Proton number / atomic number
• Which number, A or Z, defines which element it is?

  Z (proton/atomic number)
• What is the definition of nucleon number?

  Total number of protons and neutrons
• Atoms have equal numbers of what two particles?

  Protons and electrons
• How do atoms become positive ions?

  They lose electrons
• How do atoms become negative ions?

  They gain electrons
• What is the magnitude of the charge on an electron/proton?

  1. 6 x 10^-19 C
• What is the mass of a nucleon?

  1. 67 x 10^-27 kg
• What is the mass of an electron?

  1. 11 x 10^-31 kg
• How do we work out the mass of an atom, ion, or nucleus in kilograms?

  Number of nucleons x 1.67 x 10^-27
• How do we work out the charge of a nucleus in coulombs?

  Number of protons x 1.6 x 10^-19
• How do we work out the charge of an ion in coulombs?

  Relative charge x 1.6 x 10^-19
• How do we calculate specific charge?

  Specific charge = charge / mass = Q / m
• What are the units for specific charge?

  C kg^-1
• What are isotopes?

  Atoms with the same number of protons and different numbers of neutrons
• True or false: isotopes have different chemical properties?

  False
• True or false: isotopes have different nuclear stability?

  True
• Describe the role of the strong nuclear force in nuclear stability.

  • Balances the electrostatic repulsion between positively charged protons<br>- Holds nucleons in an equilibrium position
• Is the strong nuclear force associated with charge?

  No – acts equally between protons and neutrons
• Describe how and explain why the strength of the nuclear force varies with nuclear separation.

  Below 0.5 fm -> repulsive; between 0.5 – 3.0 fm -> attractive; beyond 3.0 fm -> zero
• What type of nuclei normally undergo alpha decay?

  Massive nuclei
• What is an alpha particle made up of?

  2 protons and 2 neutrons (helium nucleus)
• Write the general alpha decay equation.

  $X \rightarrow Y \quad A-4 \quad Z-2 +$$\alpha$
• What type of nuclei normally undergo beta minus decay?

  Neutron-rich nuclei (high neutron to proton ratio)
• What is a beta minus particle?

  An electron
• Describe the change in the nucleons during beta minus decay.

  A neutron changes into a proton

  
• Name the extra particle emitted in beta minus decay.

  Electron anti-neutrino
• Why did scientists hypothesize the extra particle in beta minus decay?

  • Total energy after the decay was less than before<br>- Missing energy must be carried away by another particle to conserve energy