atomic structure

• What is the charge of the nucleus?

  Positively charged
• What particles are found 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?

  $1 \times 10^{-10} \text{ metres}$
• Where is most of the mass of an atom concentrated?

  At the nucleus
• How does the radius of the nucleus compare to the radius of an atom?

  The nucleus is 10,000 times smaller
• 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 interaction
• 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 with same protons but different neutrons
• Give an example of isotopes of carbon.

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


  Proton number
• What does the symbol $A$ represent in isotopes?


  Mass number (neutrons + protons)
• What does the symbol $N$ represent in isotopes?


  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?

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

  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 atoms in 1911?

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

  Most alpha particles passed through

  
• What did slight deflections of alpha particles indicate?

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

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

  The final model of the atom
• What did Chadwick prove about the nucleus?

  Neutrons exist in the nucleus
• What is radioactive decay?

  Random process of unstable nuclei changing
• How is activity measured?

  In Becquerel, Bq
• What does a high activity indicate?

  Fast rate of decay
• What is count-rate?

  Number of decays recorded per second
• What is alpha decay?

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

  Highly ionising
• How penetrating is alpha radiation?

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

  Emission of an electron
• How ionising is beta radiation?

  Medium ionising