Atomic Structure

• Who proposed the atomic theory that atoms of an element are identical and cannot be divided?

  John Dalton
• What did J.J. Thomson's cathode-ray tube experiment demonstrate about atoms?

  Atoms contain small particles (electrons) and can be split
• What model did J.J. Thomson propose for the structure of the atom?

  Plum pudding model
• What did Rutherford's gold foil experiment reveal about the structure of the atom?

  Atoms have a small, dense, positively charged nucleus
• Who proposed that electrons occupy shells around the nucleus?

  Niels Bohr
• What was the significance of Geiger and Marsden's gold foil experiment?

  It led to the discovery of the atomic nucleus
• What is the typical size (order of magnitude) of atoms and small molecules?

  $10^{-10}$ meters
• What is the relative charge of a proton?

  +1
• What is the relative mass of a neutron?

  1
• What is the relative mass of an electron?

  1/1836
• If an atom has an atomic number of 6 and a mass number of 12, how many neutrons does it have?

  6
• If an ion has a charge of +2 and an atomic number of 12, how many electrons does it have?

  10
• What is the difference between an atom and an ion?

  An ion has a charge due to lost or gained electrons
• What is the definition of an isotope?

  Atoms of the same element with different numbers of neutrons
• If an isotope has an atomic number of 8 and a mass number of 16, how many protons, neutrons, and electrons does it have?

  8 protons, 8 neutrons, 8 electrons
• Why is the nuclear radius much smaller than the radius of the atom?

  Most of the atom's volume is empty space with electrons orbiting
• What is the charge of the nucleus of an atom?

  Positive
• What is the charge of the electrons surrounding the nucleus?

  Negative
• Why do small molecules have a larger size than individual atoms?

  Small molecules are made up of multiple atoms bonded together
• What is the mass number of an atom?

  Number of protons + number of neutrons
• If an ion has a charge of -1 and an atomic number of 17, how many electrons does it have?

  18
• What does the atomic number of an element represent?

  Number of protons in the nucleus
• What is the relative charge of a neutron?

  0
• If an atom has an atomic number of 20 and a mass number of 40, how many neutrons does it have?

  20
• Why do isotopes of the same element have the same chemical properties?

  They have the same number of protons and electrons
• What is the relative mass of a proton?

  1
• If an ion has a charge of +3 and an atomic number of 13, how many electrons does it have?

  10
• Why is the mass of an atom concentrated in the nucleus?

  Protons and neutrons are much heavier than electrons
• What is the relative charge of an electron?

  -1
• If an atom has an atomic number of 7 and a mass number of 14, how many neutrons does it have?


  7
• Why do atoms have no overall charge?

  Number of protons equals number of electrons
• What is the definition of an ion?

  An atom with a positive or negative charge
• If an ion has a charge of -2 and an atomic number of 8, how many electrons does it have?

  10
• Why do isotopes have different mass numbers?

  They have different numbers of neutrons
• What is the relative mass of a neutron?

  1
• If an atom has an atomic number of 11 and a mass number of 23, how many neutrons does it have?

  12
• Why do ions have a charge?

  They have lost or gained electrons
• What is the relative charge of a proton?

  +1
• If an ion has a charge of +1 and an atomic number of 19, how many electrons does it have?

  18
• Why do atoms of the same element have the same atomic number?

  They have the same number of protons