Science ( atomic structure)

• What is the charge of the nucleus?

  Positively charged
• What particles are contained in the nucleus?

  Neutrons and protons
• What is the charge of electrons?

  Negatively charged
• What is the relative mass of a proton?

  1
• What is the relative charge of a neutron?

  0
• What is the typical radius of an atom?

  $1 \times 10^{-10} \text{ metres}$
• How much smaller is the radius of the nucleus compared to the atom?

  10,000 times smaller
• Where is most of the mass of an atom concentrated?

  At the nucleus
• What is the arrangement of electrons in an atom?

  • Electrons lie at different distances from the nucleus
  • They occupy different energy levels
  • Arrangements may change with EM radiation
• What do all atoms of the same element have in common?

  Same number of protons
• What defines a neutral atom?

  Same number of electrons and protons
• What are isotopes?

  Atoms of the same element with different masses
• Give an example of isotopes of carbon.

  Carbon-12, Carbon-13, Carbon-14
• What does the symbol X represent in isotopes?

  The letter of their element
• What does the mass number A represent?

  Number of neutrons and protons
• What does the proton number Z represent?

  The number of protons
• What does N represent in atomic notation?

  The charge of the atom
• What happens to the charge of an atom if there are more electrons than protons?

  It becomes negatively charged
• What happens to the charge of an atom if there are fewer electrons than protons?

  It becomes positively charged
• What occurs when electrons change orbit?

  They absorb or emit EM radiation
• What happens when electrons move to a higher orbit?

  The atom absorbs EM radiation
• What happens when electrons fall to a lower orbit?

  The atom emits EM radiation
• What can happen if an electron gains enough energy?

  It can leave the atom, forming a positive ion
• What did Dalton propose about atoms in 1800?

  Everything was made of tiny spheres
• Who discovered the electron in 1897?

  JJ Thomson
• What was the Plum Pudding Model?

  Electrons dispersed in positive "pudding"
• What did Rutherford realize about the atom in 1911?

  Most of the atom was empty space
• What did the Gold Foil Experiment demonstrate?

  Most alpha particles passed through

  
• What did slight deflections of alpha particles indicate?

  The nucleus must be charged
• What did large deflections of alpha particles suggest?

  The nucleus contains most of the mass
• What model did Bohr produce in 1913?

  The final model of the atom
• What did Chadwick provide evidence for?

  Existence of neutrons
• What is radioactive decay?

  • Random process of unstable nuclei changing
  • Nucleus emits radiation to become stable
• What is activity in terms of radioactive decay?

  Rate of decay of unstable nuclei
• How is activity measured?

  In Becquerel, Bq
• What is count-rate?

  Number of decays recorded per second
• What are the forms of radioactive decay?

  • Alpha (α): Highly ionising, weakly penetrating
  • Beta Minus (β): Medium ionising, medium penetration
  • Gamma (γ): Low ionising, highly penetrating
  • Neutrons: Not specified
• What is alpha decay?

  Emission of a helium nucleus
• How penetrating is alpha radiation?

  Weakly penetrating (~5cm of air)
• What is beta minus decay?

  Emission of an electron