chemistry 2a- bonding and calculations

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  • Created by: shona
  • Created on: 29-12-12 15:03
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  • chemistry 2a- bonding and calculations
    • atoms compounds and isotopes
      • atoms
        • contains protons neutrons and electrons
        • atomic number and mass number describe the atom
          • mass number
            • the top number on this symbol tells you the total number of protons and neutrons
          • atomic number
            • the bottom number tells you the number of protons
        • the atomic number tells you how many protons there are
        • atoms of the same element all have the same number of protons so atoms of different elements will have different numbers of protons
        • to get the number of neutrons subtract the atomic number from the mass number
          • electrons aren't counted in the mass number because their relative mass is very small
      • compounds
        • compounds are chemically bonded
        • compounds are formed when 2 or more elements are chemically combined together
        • for example carbon dioxide is a compound formed from a chemical reaction between carbon and oxygen
        • it is difficult to separate the two original elements again
      • isotopes
        • isotopes are the same except for an extra neuron or two
        • DEFINITION: ISOTOPES ARE DIFFERENT ATOMIC FORMS OF THE SAME ELEMENT WHICH HAVE THE SAME NUMBER OF PROTONS BUT A DIFFERENT NUMBER IF NEUTRON
        • isotopes must have the same atomic number but different mass number
        • if they have different atomic numbers they'd be different elements altogether
        • carbon 12 and carbon 14 are a very popular pair of isotopes
    • ionic bonding
      • atoms lose or gain electrons to form charged particles(ions) which are strongly attracted to one another( because of the attraction of opposite charges + and -)
      • all the atoms on the left side of the periodic table only have one or two electrons on their outer shell so they are keen to get rid of them
        • meaning they will have a full outer shel
      • when they get rid of the electrons the atoms become ions instead
      • now they are ions they like to join with other ions of the opposite charge and stick to it like glue
      • on the right side of the periodic table the elements outer shell is nearly full so they want go gain electrons to make a full outer shell
      • when they become an ion they latch on to the atom that gave them the electrom
      • ionic compound have a regular lattice structure
        • ionic compounds always have giant ionic lattices
        • the ions form a closely packed regular lattice arrangement
        • there are very strong electrostatic forces of attraction between oppositely charges ions in all directions
      • ionic compounds all have similar properties
        • high melting and boiling points due to the strong attractions between ions
          • takes a large amount of energy to overcome this attraction
          • when ionic compounds melt they are free to move and they'll carry electric current
        • they dissolve easily in water
          • the ions separate and are free to move in the solution so they'll carry electric current
    • ions and formula
      • groups 1 and 2 and 6 and 7 are most likely to form ions
      • atoms that have lost or gained electrons are ions
      • ions have the electronic structure of a noble gas
      • group 1 and 2 are metals they lose electrons to form a positive ion
      • group 6 and 7 are non-metals they gain electrons to form negative ions
      • the charge on positive ions is the same as the group number of the element
      • only the elements at the opposite sides of the periodic table will form ionic compounds
  • remember to give is positive and to take is negative

Comments

Lorran payne

Thanks this was very useful for my revision as i am rubbish at bonding and calculations

Josh747

A lot of useful information.

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