Chemistry Unit 3

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Chemistry Unit 3
2010-04-18 17:50:35
Chemistry GCSE

How was the periodic table developed and how can it help us understand the reactions of elements? What are the strong and weak alkalis? How can we find the amounts of acids and alkalis in solutions? What is in the water we drink? How much energy is involved in chemical reactions? How do we identify and analyse substances?
Show Answers:

  1. In the modern periodic table, how are the elements arranged?
    In order of atomic number
  2. In the periodic table, what do groups order?
    Elements with similar chemical properties
  3. Why is the periodic table not ordered by reletive atomic mass?
    It would result in some oddities (such as argon ending up in group 1 instead of group 8)
  4. What is the periodic table an arrangement of?
    Elements in terms of their electronic structure
  5. What must elements in the same group have, in turms of their electronic structure?
    The same number of electrons in thier outermost shell
  6. What happens to the electronic structure of elements as you go along a period (row)?
    An electron is added each time, gradually filling the energy level.
  7. Where can non-metals be found on the modern periodic table?
    On the right hand side of the table
  8. What did John Newlands (1864) order elements by?
    Their reletive atomic mass
  9. What did Dimitri Mendeleev do to the periodic table when he realised not all elements had been discovered?
    He left gaps to accomodate them
  10. What is group 1 known as in the periodic table?
    The alkali metals
  11. What happens as we go down in a group in the periodic table?
    The elements become more reactive the further you go down (eg. 6th element is more reactive than the 3rd in the group)
  12. What happens to the melting and boiling points of alkali metals as you go further down the group?
    It decreases
  13. Do alkali metals have a high or low melting point?
  14. Why are alkali metals stored under oil?
    They react vigerously with oxygen and water
  15. What is the equation for when an alkali metal reacts with water (in this example potassium)
    Potassium + Water ---> Potassium hydroxide + Hydrogen

    2K(s) + 2H2O(l) ---> 2KOH (aq) + H2
  16. What type of compound is formed when alkali metals react with non-metals?
    Ionic compound
  17. What happens to the alkali metal atom when it reacts with a non-metal?
    It looses an electron to form a metal ion with a POSITIVE charge
  18. What is the equation for when an alkali metal reacts with a non-metal (in this example sodium and chlorine)
    Sodium + Chlorine ---> Sodium Chloride

    2Na(s) + Cl2(s) ---> 2Na+Cl-(aq)
  19. How many elements are in the alkali metals?
  20. How many halogens are there?
  21. What are the elements in group 7 in the periodic table known as?
    The halogens
  22. What happens to the reactivity of halogens as you go down the group?
    It decreases (eg. 3rd element more reactive than 6th element)
  23. What happens to the melting and boiling points of halogens as you go down the group?
    It increases (eg. 2nd element has a lower boiling point than 5th element)
  24. Name THREE quialities of halogens?
    • Brittle and crumbly when solid
    • Poor conductors of heat and electricity
    • At room temperature, they are generally liquid
    • They have colourless vapours
  25. When halogens react with metals what is produced
    Ionic salts
  26. What happens to the electronic structure of a halogen in a reaction with a metal?
    The halogen atom gains one electron to form a halogen ion with a charge of -1