Atoms and Isotopes

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

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

  In the nucleus
• What are the three subatomic constituents of an atom?

  Proton, neutron, electron
• Explain how an atoms electron arrangement changes when it absorbs EM radiation

  • Electrons move further away from the nucleus
  • They move to a higher energy level
• How do atoms turn into positive ions?

  • They lose one or more of their outer electrons
  • Electrons are negatively charged, so the resultant charge of atom is positive
• What is an isotope of An atom?

  An atom of a element that has a different number of neutrons but the same number of protons
• What is an atoms mass number?

  The total number of protons and neutrons in the atom.
• What is the name given to the number of protons in an atom?

  Atomic number
• What do all forms of the same element have in common?

  They all have the same number of protons
• How does the ratio of electrons to protons in an atom result in the atom having overall charge?

  • the number of protons is equal to the number of electrons
  • Protons and electrons have equal and opposite charges, so charge cancles out.
• What type of charge does the nucleus of the atom have? why?

  • positive charge
  • The nucleus contains protons and neutrons
  • Protons have positive charge
  • Neutrons have netural charge
• Describe the arrangement of protons, neutrons and electrons in an atom.

  • Protons and neutrons are found in the atoms nucleus
  • The electrons are found in discrete energy levels around the nucleus
• Approximately what proportion of the total radius of an atom is the radius of the nucleus?

  1/10,000
• Give two ways an atoms electron arrangement can be changed.

  • absorbing electromagnetic radiation
  • emitting electromagenetic radiation
• What may lead to a scientific model being chcanged or replaced?

  The discovery of new experimental evidence which doesnt agree with the exisiting theory
• How did the plum-pudding model describe the atom?

  A ball of positive charge, with negatively charged electrons distrubeted evenly throughout it.
• What is the name given to the currently accepted model of the atom?

  The Bohr Nuclear Model.
• Prior to the discovery of electron, what was believed about the atom?

  The atom was believed to be indivisible.
• State the conclusions of the alpha-scattering experiment.

  • Most of the mass of the atom is concentrated in the nucleus
  • The nucleus is positivitely charged.
• What reinforces a scientific theory?

  When experimental results agree with the hypothesised theoretical calculations and theories.
• What did James Chadwicks experiments on the atoms prove?

  Existence of the neutron