Atoms and Isotopes

• What is an approximation for the radius of an atom?

  $1 \times 10^{-10} \text{ metres}$
• What are the three subatomic constituents of an atom?

  • Proton
  • Neutron
  • Electron
• Where is most of the mass of an atom concentrated?

  In the nucleus
• What proportion of the total radius of an atom is the radius of the nucleus?

  $\frac{1}{10,000}$
• Describe the arrangement of protons, neutrons, and electrons in an atom.

  • Protons and neutrons are in the nucleus
  • Electrons are in discrete energy levels around the nucleus
• What type of charge does the nucleus of an atom have and why?

  Positive charge due to protons
• How can an atom's electron arrangement be changed?

  1. Absorbing electromagnetic radiation
  2. Emitting electromagnetic radiation
• How does an atom's electron arrangement change when it absorbs EM radiation?

  Electrons move to a higher energy level
• How does an atom's electron arrangement change when it emits EM radiation?

  Electrons move to a lower energy level
• How does the ratio of electrons to protons result in an atom having no overall charge?

  Equal number of protons and electrons
• What do all forms of the same element have in common?

  They all have the same number of protons
• What is the name given to the number of protons in an atom?

  Atomic Number
• What is an atom's mass number?

  Total number of protons and neutrons
• What is an isotope of an atom?

  Different number of neutrons, same protons
• How do atoms turn into positive ions?

  They lose one or more outer electrons
• What may lead to a scientific model being changed or replaced?

  New experimental evidence contradicting existing theory
• How did the plum-pudding model describe the atom?

  the electrons were embedded in a uniform sphere of positive charge
• What was believed about the atom before the discovery of the electron?

  The atom was believed to be indivisible
• Which experiment led to the plum-pudding model being discarded?

  Rutherford’s alpha-scattering experiment
• What is the name given to the currently accepted model of the atom?

  The Bohr nuclear model
• What are the conclusions of the Alpha-Scattering experiment?

  • Most mass is in the nucleus
  • The nucleus is positively charged
• What reinforces a scientific theory?

  Experimental results that agree with theoretical calculations
• What did James Chadwick’s experiments on the atom prove?

  The existence of neutrons
• What is the order of the history of an atom timeline

  Dragonflies Teach Rabbits Breakdancing Classes!

  Dalton (1803) --> Billiard Ball model

  Thomson (1897) --> Plum Pudding Model

  Rutherford (1909-1911) --> Rutherford Model

  Bohr (1913) --> Nuclear model

  Chadwick (1932) --> Nuclear Model