Atomic Structure

• What is the charge of the nucleus in an atom?

  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 does the radius of the nucleus compare to the radius of an atom?

  The nucleus is 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?

  The same number of protons
• What defines a neutral atom?

  It has the same number of electrons and protons

  
• What are isotopes?

  Atoms with the same protons but different neutrons
• What does the letter X represent in the notation $^{A}_{Z}X$?


  The letter of the element
• What does A represent in the notation $^{A}_{Z}X$?


  The mass number (protons + neutrons)
• What does Z represent in the notation $^{A}_{Z}X$?


  The proton number
• What does N represent in the notation $^{A}_{Z}X$?


  The charge of the atom
• What happens to the charge of a neutral atom if it has more electrons than protons?

  It becomes negatively charged

  
• What happens to the charge of a neutral atom if it has fewer electrons than protons?

  It becomes positively charged

  
• What occurs when electrons change orbit in an atom?

  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
• Who proposed that everything was made of tiny spheres in 1800?

  Dalton
• What did JJ Thomson discover in 1897?

  The electron
• What model was formed after the discovery of the electron?

  The Plum Pudding Model
• What did Rutherford realize about the atom in 1911?

  Most of the atom is empty space
• What experiment did Geiger and Marsden conduct?

  The Gold Foil Experiment
• What did the Gold Foil Experiment demonstrate?

  Most of the atom is empty space
• What happens to alpha particles in the Gold Foil Experiment?

  Most pass through, some deflect

  
• What does deflection of alpha particles indicate?

  The nucleus must be charged
• What does a deflection greater than 90° suggest?

  The nucleus contains most of the mass
• What did Bohr contribute to atomic theory in 1913?

  The final model of the atom
• What was discovered about the positive charge of the nucleus?

  It can be subdivided into protons
• Who provided evidence for neutrons?

  James Chadwick
• What is radioactive decay?

  A random process of nucleus changing
• What is activity in terms of radioactive decay?

  The rate of unstable nuclei decaying
• How is activity measured?

  In Becquerel, Bq
• 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