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Chemistry Paper 1 - Coggle Diagram
Chemistry Paper 1
C2 - bonding, structure and properties of matter
ionic bonding
when a metal and non-metal react together, the metal atom loses electrons to form a positively charged ion and the non-metal gains these electrons to form a negatively charged ion
for example to make sodium chloride (NaCl), the sodium atom gives up its outer electron becoming an Na+ ion and the chlorine atom picks up the electron putting it on its outer shell becoming a Cl- ion
ionic compounds have a structure called a giant ionic lattice and the ions form a closely packed regular lattice arrangement with very strong electrostatic forces between oppositely charged ions in all directions in the lattice
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to work out the empirical formula of an ionic compound from a diagram of the compound - if its a dot and cross diagram, count up how many atoms there are of each element
covalent bonding
when non-metal atoms bond together, they share pairs of electrons to make covalent bonds and the positively charged nuclei of the bonded atoms are attracted to the shared pair of electrons by electrostatic forces making covalent bonds very strong -- atoms only share electrons in their outer shells - each single covalent bond provides one extra shared electron for each atom - each atom involved generally makes enough covalent bonds to fill up its outer shell - covalent bonding happens in non-metals and compounds of non-metals
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simple molecular substances are made up of molecules containing a few atoms joined together by covalent bonds - some examples are hydrogen(H2), chlorine(Cl2), oxygen(O2), nitrogen(N2) etc.
polymers are lots of small units linked together to form a long molecule that has repeating sections and all the atoms in a polymer are joined by strong covalent bonds
allotropes of carbon
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diamond has a giant covalent structure made up of carbon atoms that each form four covalent bonds covalent bonds making diamond really hard - the strong covalent bonds take a lot of energy to break and give it a very high melting point - it doesn't conduct electricity because it has no free electrons or ions
in graphite, each carbon atom only forms three covalent bonds, creating sheets of carbon atoms arranged in hexagons - there aren't any covalent bonds between the layers (they're only held together weakly, so they're free to move over each other this making graphite soft and slippery so it's ideal as a lubricant -- graphites got a high melting point and the covalent bonds in the layers need loads of energy to break - only 3 out of each carbon's 4 outer electrons are used in bonds, so each carbon atom has one electron that's delocalised and can move therefore graphite can conduct electricity and thermal energy
metallic bonding
metals also consist of a giant structure and the electrons in the outer shell of the metal atoms are delocalised (free to move). There are strong electrostatic forces between the positive metal ions and the shared negative electrons. These forces of attraction hold the atoms together in a regular structure and are known as metallic bonding - substances that are held together by metallic bonding include metallic elements and alloys - it's the delocalised electrons in the metallic bonds which produce all the properties of metals
the electrostatic forces between metal atoms and the delocalised sea of electrons are very strong, so need lots of energy to be broken -- this means that most compounds with metallic bonds have very high melting and boiling points so they're generally solid at room temp
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most metals are malleable due to the layers of atoms being able to slide over each other and this also means they can be bent or hammered or rolled into flat sheets
states of matter
there are three different forms - solid, liquid and gas
you can use the particle theory to show how the particles in a material behave in each of the three states of matter
in solids, there are strong forces of attraction between particles and can't move from their fixed positions but they do vibrate
in liquids, there is a weak force of attraction and are randomly arranged with the freedom to move past each other but tend to stay close. Also having a fixed volume but can change shape
in gases, the force of attraction is very weak between particles and therefore free to move and are far apart - can change shape and volume with random movement of the particles
changing state: solid to liquid (melting) - liquid to solid (freezing) - liquid to gas (boiling) - gas to liquid (condensing)
to predict the state of a substance at a certain temperature - if the temperature's below the melting point then its a solid - if it's above the boiling point then its a gas - if it's inbetween the two points then its a liquid