C3 Structure and Bonding

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C3.1: States of Matter

  • the three states of matter are solid, liquid and gas.
  • the particles in a solid are packed closely together and vibrate around fixed positions
  • the particles in a liquid are also close together but can slide over each other in random motion.
  • the particles in a gas have a lot of space between them and zoom around randomly
  • in melting and boiling, energy is transferred from the surroundings to the substance
  • in freezing and condensing, energy is transferred from the substance to the surroundings. 
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C3.2: Atoms into Ions

  • elements react together to form compounds by gaining, losing  or sharing electrons
  • the elements in group 1 react with the elements in group 7
  • as they reach, each atom of group 1 can lose one electron to gain stable electronic structure of a noble gas.
  • this electron can be given to a group 7 element, which also achieves the stable electronic structure of a noble gas.
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C3.3: Ionic Bonding

  • ionic compounds are held together by strong forces of attraction between their oppositely charged ions
  • this is called ionic bonding
  • apart from the elements in groups 1 and 7, other elements can form ionic compounds, such as those from groups 2 and 6, forming 2+ and 2- ions respectively
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C3.4: Giant Ionic Structures

  • a lot of energy is needed to break the many strong ionic bonds, which operate in all directions and form a giant ionic lattice
  • ionic compounds have high melting points and are solid at room temperature
  • ionic compounds will conduct electricity when molten or dissolved in water
  • this is because their ions can move around and carry charge through the liquid.
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C3.5: Covalent Bonding

  • covalent bonds are formed when atoms of non-metals share pairs of electrons with each other
  • each shared pair of electrons is a covalent bond
  • many substances containing covalent bonds consist of simple molecules but some have giant covalent structures
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C3.6: Structure of Simple Molecules

  • substances made up of simple molecules have low melting and boiling points
  • the intermolecular forces are weak and explain why they have such low boiling and melting points
  • simple molecules have no overall charge so cannot carry electrical charge
  • substances made of simple molecules do not conduct electricity.
  • models are used to help understand bonding but each model has its limitations
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C3.7: Giant Covalent Structures

  • some covalently bonded substances have giant structures
  • these have very high melting and boiling points
  • graphite contains giant layers of covalently bonded carbon atoms
  • there are no covalent bonds between the layers which means they can slide over each other.
  • the carbon atoms in diamod have a rigid giant covalent structure making it a very hard substance
  • graphite can conduct electricity and thermal energy because of the delocalised electrons that can move along the layers. 
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C3.8: Fullerenes and Graphene

  • carbon also exists as fullerenes, which can form large cage-like structures and tubes, made of hexagonal rings of carbon atoms
  • the fullerenes are used as transport mechanisms for drugs to specific body sites, catalysts and reinforcement for composite  materials
  • graphene is a single layer of graphite and is one atom thick
  • it has high electrical conductivity and will help create developments in the electronics industry 
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C3.9: Bonding in Metals

  • the atoms in metals are closely packed together and arranged in regular layers
  • metallic bonding is positively charged metal ions, held together by electrons from the outermost shell of each metal atom
  • the delocalised electrons are free to move throughout the giant metallic lattice. 
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C3.10: Giant Metallic Structures

  • metals can be bent and shaped because the layers of atoms in a giant metallic structure can slide over each other
  • alloys are harder that pure metals because the regular layers in a pure metal are distorted by atoms of different sizes in an alloy
  • delocalised electrons in metals enable electricity and thermal energy to be transferred through a metal easily 
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