gcse chemistry periodic table

• The modern periodic table approximately lists 100 elements
• The periodic table has changed a lot over time as scientists have organised the elements differently
• The modern periodic table approximately lists 100 elements
• The periodic table has changed a lot over time as scientists have organised the elements differently
• Dmitri Mendeleev


  Founder of the 1st periodic table
• The first list of elements, Mendeleev's table and the modern periodic table

  Have differences
• How the elements are ordered in the forms of the periodic table

  • 1st list - by atomic mass
  • Mendeleev - normally by atomic mass but some elements were swapped around
  • Modern - by atomic number
• Gaps in the different forms of the periodic table

  • 1st list - no gaps
  • Mendeleev - gaps left for undiscovered elements
  • Modern - no gaps, all elements up to a certain atomic number have been discovered
• How the elements are grouped in the different forms of the periodic table

  • 1st list - not grouped
  • Mendeleev - grouped by chemical properties
  • Modern - grouped by the number of electrons in the outer shells
• Placement of non-metals and metals in the different forms of the periodic table

  • 1st list - no clear distinction
  • Mendeleev - no clear distinction
  • Modern - metals to the left, non-metals to the right
• Problems in the different forms of the periodic table

  • 1st list - some elements grouped inappropriately
  • Mendeleev - incomplete, with no explanation for why some elements had to be swapped to fit in the appropriate groups
  • Modern - no problems
• Mendeleev's ability to accurately predict properties of undiscovered elements


  Based on the positions of the gaps in the table
• The discovery of electrons allowed scientists to work out that elements with the same number of electrons in their outer shell had similar chemical properties
• The discovery of protons allowed scientists to order the elements by atomic number
• The discovery of neutrons led to the discovery of isotopes, which explained why some elements didn't fit when the periodic table was ordered by atomic mass
• Group 0 elements


  Noble gases
• Noble gases


  • Have a full outer shell, are very unreactive (inert) so exist as single atoms as they do not bond to form molecules, have boiling points that increase down the group
• What group 1 metals react with

  • Water, oxygen and chlorine
• Reactions of alkali metals with water, oxygen and chlorine

  1. Lithium + oxygen = lithium oxide

  2. Lithium + chlorine = lithium chloride

  3. Lithium + water = lithium hydroxide + hydrogen
• Group 1 elements


  Alkali metals because they react with water to form an alkali (a solution of their metal hydroxide)
• Reactivity of group 1 elements

  Very reactive because they only need to lose 1 electron to react (only 1 electron in outer shell)
• Reactivity in group 1

  Increases down the group
• Reactivity increasing down group 1

  The atoms increase in size, the outer electron is further away from the nucleus and there are more shells shielding the outer electron from the nucleus, the electrostatic attraction between the nucleus and the outer electron is weaker, so it is easier to lose one electron
• Melting point and boiling point in group 1

  Decrease down the group
• Group 7 elements


  The halogens
• Group 7 elements


  • They are non-metals that exist as molecules made up of pairs of atoms
• Melting point and boiling point in group 7

  Increase down the group
• Reactivity in group 7


  Decreases down the group
• Elements in group 7 existing as pairs of atoms


  • Fluorine is F2 and chlorine is Cl2
• States of the different elements in group 7

  • Fluorine and chlorine = gas, bromine -liquid, iodine-solid
• Reactivity decreasing down group 7


  The atoms increase in size, the outer shell is further from the nucleus and there are more shells shielding the outer electron from the nucleus, the electrostatic attraction from the nucleus to the outer shell is weaker, so it is harder to gain the one electron to fill the outer shell
• Displacement


  More reactive elements can take the place of less reactive ones in a compound
• Reaction: fluorine + potassium chloride

  Potassium fluoride + chlorine
• Transition metals


  Found in the middle of the periodic table, have similar properties to each other
• Comparison of group 1 metals and transition metals

  • Melting points - group 1 relatively low, transition metals relatively high
  • Density - group 1 relatively low, transition metals relatively high
  • Strength - group 1 relatively low, transition metals relatively high
  • Hardness - group 1 relatively low (easy to scratch), transition metals relatively high (hard to scratch)
  • Reactivity with halogens, oxygen and water - group 1 reacts easily, transition metals react slowly if at all
• Transition metals


  Very useful as catalysts
• When transition metals take on a compound, they often take on a colour
• Reaction of group 1 metals with water

  2Na + 2H2O = 2NaOH + H2
• Reaction of group 1 metals with oxygen

  4Na + O2 = 2Na2O
• Reaction of group 1 metals with halogens

  2Na + Cl2 = 2NaCl