Chemistry term 1 year10

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  • Chemistry
    • What's an element? How many are there and where can we find them?
      • Elements are substances which contain only 1 type of atom.
      • There are 118 elements and we know that from the periodic table.
    • What's an atom?
      • Atoms are the smallest particle of matter to 'exist'.
    • When elements combine together what new substance is formed?
      • A chemical compound- a substance made up of two or more different elements chemically bonded together.
      • Often the compound will have different properties from the elements that make it.
    • What is the ending of a compound which has a metallic element & a non-metallic element combined within it?
      • Ide
      • When a compound ends in ate it is because it has 2 non-metallic and 1 metallic and one of the non-metallic is Oxygen.
    • How do electrons orbit the nucleus of an atom?
      • Electrons (negative) move in distinct energy levels where they move around the nucleus that's made up of protons (positive) & neutrons(neutral).
    • What is the bigger no. next to an elements symbol known as?
      • The atomic mass no. it tells us the no. of protons and neutrons where the small no. (atomic no.) just tells us the no. of protons.
    • How does the electron configuration go?
      • 2,8,8,8,18.
        • Elements within the same group-vertical columns-have the same no. of electrons in their highest energy level.
        • The horizontal rows called periods tell us how many energy levels each element has.
    • What is a noble gas?
      • Elements that have a full outer shell without reacting with anything they are stable and unreactive.
        • Elements want to have the same configuration as the nearest noble gas to them on the table. 1 way to do this is physical transfer of electrons from 1 element to another. This is ionic bonding.
          • When an atom loses an electron that electron joins an element that needs it to become stable. An ion has a charge where as an atom is neutral. It becomes an ion when it undergoes ionic bonding.
            • What are the rules for ionic bonding?
              • 1) Metals always lose electrons (electron donors) then the ion has a positive charge equal to the number of electrons the metal has lost.
                • 5) We can use ionic formulae to calculate the formulae of an ionic compound.
              • 2) Non-metals always gain electrons. Then the ion has a negative charge equal to the number of electrons the non-metal has gained.
              • 3) Ionic compounds have to be neutral overall.
                • 4) An ion is defined as a charged atom/group of atoms.
                • 6) An ionic bond is the electro-static force of attraction between a positive metal ion and a negative non-metal ion.
    • Co-valent bonding
      • Electrons in this bonding are never transferred but shared between the participating elements which are usually non-metals.
      • Non-metal atoms can achieve a stable octet(full outer shell) by sharing electrons with other non-metals.
    • Limestone(a sedimentary rock)
      • Calcium Carbonate CaCO3. With high temp. & pressure-marble, high pressure-limestone, low pressure-chalk.
        • Metal carbonates will be eroded by acid rain as it reacts with it.
          • CaCO3 +2HCl~ CaCl2 + H2O +CO2
      • When CaCO3 is bubbled through limewater and if it turns clear to cloudy we know that CO2 is present. This test produces an insoluble solid within a liquid (precipitation reaction).
      • CaCO3 can under go thermal decompositio-n where a substance is broken down by heat. All metal carbonates thermally decompose when heated. Due to heat being taken in it's an endothermic reaction.
      • Calcium oxide + H2O makes Calcium Hydroxide (slaked lime) heat is given out to do this making it an exothermic reaction. Note that hydroxides are always alkaline.


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