atomic structure

• what did John Dalton describe the atom as?

  solid spheres and different spheres made up the different elements
• who said that solid spheres and different spheres made up the different elements?

  John Dalton
• who created the first model of the atom?

  John Dalton
• what did JJ Thompson discover from his measurements of charge and mass?

  that an atom must contain even smaller, negatively charged particles, electrons. The idea of the solid sphere atomic structure had to be changed
• what was JJ Thompson's model called?

  Plum pudding model.
• who came up with the plum puddig model?

  JJ Thompson
• what did Niels Bohr suggest about the structure of atoms?

  Electrons can only exist in fixed orbits, or shells, and not anywhere in between. Each shell has a fixed energy.
• what was Bohr's theory of atomic structure supported by?

  By many experiments and it helped to explain lots of other scientist's observations at the time. It was close to our currently accepted version of the atom.
• what is the relative mass of a proton?

  1
• what is the relative mass of a neutron?

  1
• what is the relative mass of an electron?

  0.0005
• what is the relative charge of a proton?

  +1
• what is the relative charge of a neutron?

  0
• in what year did Mendeleev arrange the periodic table?

  1869
• how did Mendeleev arrange the periodic table in rows?

  in rows by increasing atomic mass, elements with lower atomic masses on the left.
• how did Mendeleev arrange the periodic table in columns?

  all elements in a column have similiar properties.
• with Mendeleev, why did some elements end up in the wrong columns?

  the atomic masses Mendeleev had was wrong (due to the pursue of isotopes) but some elements just didn't fit the pattern.
• why did Mendeleev have to leave gaps?

  to keep elements with similar properties together. He used properties of the other elements in the columns with gaps to predict properties of the undiscovered.
• what are the metals in ground 1 and 2 called?

  reactive metals
• what are the elements in group 0 called?

  noble gases
• what are the elements in group 7 called?

  halogens.
• what does the group that an element belongs to correspond to?

  the number of electrons it has in its outer shell.
• how many electrons do elements in group 0 have in their outer shell?

  full outer shells of 8 electrons (except helium which has 2).
• what does the period that an element belongs to correspond to?

  the number of shells of electrons it has.
• how many electrons are allowed in the first 3 shells?

  2, 8, 8
• what was expected to happen during the gold foil experiment?

  the particles pass right through the sheet or be slightly deflected at most.
• what actually happened during the gold foil experiment?

  most of the particles did go straight through the god sheet, some were deflected more than expected, a small number were deflected backwards.
• what did Rutherford discover as a result of the gold foil experiment?

  nuclear atom, there is a tiny, positively charged nucleus at the centre, surrounded by a cloud of negative electrons, but its mostly empty space.
• who proposed the new model of the atom where all the electrons were contained in shells?

  Niels Bohr
• what did JJ Thompson say about the model of the atom?

  atoms contain even smaller negatively charged particles, electrons. Atoms are not solid spheres, this is the Plum Pudding model.
• who performed the gold foil experiment and when?

  Ernest Rutherford, 1909
• what was the gold foil experiment?

  firing positively charged alpha particles at an extremely thin sheet of gold.
• why was Rutherford's model of the atom proved incorrect?

  the electrons in a cloud around the nucleus of an atom would be attracted to the nucleus, causing the atom to collapse.
• what is an isotope?

  different forms of the same element which have the same number of protons but different number of neutrons.
• what happens if an element only has 1 isotope?

  its relative atomic mass will be the same as its mass number.
• what happens if an element has more than 1 isotope?


  its relative atomic mass is the average of the mass numbers of all the different isotopes, taking into account how much there is of each one.
• how do you work out the relative atomic mass of an element from its isotopic abundances?

  1, multiply each relative isotopic mass by its isotopic abundance and add them.

  2, divide by the sum of the abundances
• what charge does an atom have?

  no charge, it's neutral as they have the same number of protons and electrons, so their charges cancel out.
• why do ions have charges but atoms do not?

  the number of protons does not equal the number of electrons
• what does an atom's atomic number tell you?

  how many protons it has.