the periodic table

• THE ATOM P1 - what was Dalton's model?

  John Dalton thought of the atom as a solid sphere that could not be divided into smaller parts. His model didn't include protons, electrons or neutrons.
• THE ATOM P1 - What is the Plum Pudding model?

  scientists experiments resulted in the discovery of sub-atomic charged particles. The first to be discovered were electrons. the discovery of electrons led to the plum pudding model of the atom - a cloud of positive charge, with negative electrons embedded in it.
• THE ATOM P1 - what is the alpha scattering experiment?

  1. scientists fired small, positively charged particles (alpha particles) at gold foil. 2. they expected the particles to go straight through the foil. 3. they were surprised that some of the alpha particles bounced back and many were deflected. 4. positive charge and mass of an atom must be concentrated in a small space at its centre - they called this the nucleus.
• THE ATOM P1 - what is the nuclear model?

  scientists replaced the plum pudding model with the nuclear model and suggested that the electrons orbit the nucleus, but not at set distances.
• THE ATOM P1 - what is the electron shell model?

  Neils Bohr calculated that electrons must orbit the nucleus at fixed distances. These orbits are called shells or energy levels.
• THE ATOM P1 - who discovered the neutron and how?

  James Chadwick - he carried out experiments that gave evidence for a particle with no charge. scientists called this the neutron.
• THE ATOM P1 - what is relative mass?

  one property of protons, neutrons, and electrons is relative mass. protons have 1, neutrons have 1 and electrons have 0.
• THE ATOM P1 - what is the size of an atom?

  1 x 10 (indices -10) m
• THE ATOM P1 - what is the relative charge of the three subatomic particles?

  proton = + 1 neutrons = 0 electron = - 1
• THE ATOM P1 - how would you work out the neutron number?

  mass number - atomic number.
• THE ATOM P1 - how many electrons can go on the first shell of an atom?

  2
• THE ATOM P1 - how many electrons can go in the second and third shell?

  8
• THE ATOM P1 - what are elements?

  they are substances made of one type of atom. each atom of an element will have the same number of protons.
• THE ATOM P1 - what are compounds?

  they are made up of different types of atoms chemically bonded together. the atoms in a compound have different numbers of protons.
• THE ATOM P1 - what is an isotope?

  atoms of the same electron can have different number of neutrons, giving them a different overall mass number, atoms of the same protons with different numbers of neutrons are called isotopes.
• THE ATOM P1 - what is a mixture?

  a mixture consists of two or more elements or compounds that are not chemically combined together.
• THE ATOM P1 - what are some ways of separating mixtures?

  filtration, crystallisation, simple distillation, fractional distillation, paper chromatography.
• THE PERIODIC TABLE P1 - how is the modern periodic table ordered?

  by atomic number.
• THE PERIODIC TABLE P1 - how were the early lists of elements ordered?

  by atomic mass.
• THE PERIODIC TABLE P1 - why did Mendeleev swap the order of some element?

  to group them by their chemical properties.
• THE PERIODIC TABLE P1 - why Mendeleev leave gaps in his periodic table?


  leave room for elements that had not yet been discovered.
• THE PERIODIC TABLE P1 - what is the name for group 1 elements?

  alkali metals.
• THE PERIODIC TABLE P1 - give the general equations for reactions of alkali metals with oxygen, chlorine, and water.

  metal + oxygen ---> metal oxide.

  metal + chlorine ---> metal chloride.

  metal + water ---> metal hydroxide + hydrogen.
• THE PERIODIC TABLE P1 - what name is given to group 7 elements?

  halogens.
• THE PERIODIC TABLE P1 - what name is given to group 0 elements?

  noble gases.
• THE PERIODIC TABLE P1 - how do the melting points of the halogens change down the group?

  increase.
• THE PERIODIC TABLE P1 - what is a displacement reaction?

  when a more reactive element takes the place of a less reactive one in a compound.
• THE PERIODIC TABLE P1 - why are the Nobel gases inert?

  they have full outer shells so do not need to lose or gain electrons.
• THE PERIODIC TABLE P1 - how do the melting points of the noble gases change down the group?

  increase.