Atomic Structure

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

  Positively charged

  
• What particles are contained in the nucleus of an atom?

  Neutrons and protons

  
• What is the relative mass of a proton?

  1
• What is the relative charge of an electron?

  • 1
• 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 radius of the nucleus is 10,000 times smaller than that of the atom
• 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 interaction with EM radiation
• What do all atoms of the same element have in common?

  They have the same number of protons
• What defines a neutral atom?

  A neutral atom has the same number of electrons and protons
• What are isotopes?

  Isotopes are atoms of the same element with different masses due to differing numbers of neutrons
• Give an example of isotopes of carbon.

  Carbon-12, Carbon-13, and Carbon-14
• In the notation $^{A}_{Z}X$, what does $X$ represent?


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


  $A$ is the total number of neutrons and protons
• What does the proton number $Z$ indicate?


  $Z$ indicates the number of protons in the nucleus
• How is the charge of a normal neutral atom calculated?

  The charge is neutral because the number of electrons equals the number of protons
• What happens if there are more electrons than protons in an atom?

  The atom has a negative charge

  
• What happens if there are fewer electrons than protons in an atom?

  The atom has a positive charge

  
• What occurs when electrons change orbit in an atom?

  Electrons moving to a higher orbit absorb EM radiation, while those falling to a lower orbit emit EM radiation
• What can happen if an electron gains enough energy?

  It can leave the atom to form a positive ion
• Who proposed that everything was made of tiny spheres called atoms in 1800?

  Dalton
• What did JJ Thomson discover in 1897?

  He discovered 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 was empty space
• What was the outcome of the Gold Foil Experiment?

  Most alpha particles went straight through, indicating that most of the atom is empty space

  
• What did the deflection of some alpha particles in the Gold Foil Experiment suggest?

  The nucleus must be charged, deflecting positive alpha particles

  
• What does alpha decay do to the mass and charge of the nucleus?

  Alpha decay causes both the mass and charge of the nucleus to decrease
• What does beta decay do to the mass and charge of the nucleus?

  Beta decay does not change the mass but increases the charge of the nucleus
• What does gamma decay do to the mass and charge of the nucleus?

  Gamma decay does not cause any change in mass or charge
• What is the definition of half-life?

  The half-life is the time taken for half the nuclei in a sample to decay
• If 80 atoms decay to 20 in 10 minutes, what is the half-life?

  5 minutes
• What characterizes a short half-life?

  A short half-life means the source is initially very radioactive but quickly becomes less so
• What characterizes a long half-life?

  A long half-life means the source remains weakly radioactive for a long period
• Why is Americium used in smoke alarms?

  It has a long half-life and is an alpha emitter, making it safe for use
• What is radioactive contamination?

  Radioactive contamination is the unwanted presence of radioactive atoms on other materials
• What is irradiation?

  Irradiation is exposing an object to nuclear radiation without making it radioactive
• Why is peer review essential for scientific reports on radiation effects?

  Incorrect measurements could lead to unsafe safety levels
• What are some sources of background radiation?

  Cosmic rays, radiation from underground rocks, nuclear fallout, and medical rays
• What unit is used to measure radiation dose?

  Sieverts (Sv)
• What is Technetium used for in medicine?

  It is used as a medical tracer with a half-life of 6 hours