Bonding

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  • Ionic bonding
    • Bonding
      • Metallic bonding
        • Within the metal lattice, the atoms lose their valence electrons and become positively charged. The valence electrons no longer belong to any metal atom and are said to be delocalisedThey move freely between the positive metal ions like a sea of electrons
          • Metallic bonds are strong and are a result of the attraction between the positive metal ions and the negatively charged delocalised electrons
            • Metals have high melting and boiling points. There are many strong metallic bonds in giant metallic structures. A lot of heat energy is needed to overcome forces and break these bond
              • Metals conduct electricity. There are free electrons available to move and carry charge. Electrons entering one end of the metal cause a delocalised electron to displace itself from the other end. Hence electrons can flow so electricity is conducted
                • Metals are malleable and ductile. Layers of positive ions can slide over one another and take up different positions. Metallic bonding is not disrupted as the valence electrons do not belong to any particular metal atom so the delocalised electrons will move with them. Metallic bonds are thus not broken and as a result metals are strong but flexible. They can be hammered and bent into different shapes without breaking
            • alloys are a mixture of two different metals. they are harder because diffrent size atoms distort the layers so they don't slide
      • Covalent bonding
        • NON-METAL AND NON-METAL
          • covalent bonding is SHARING of electrons to create a full outer shell
            • Covalent bonds between atoms are very strong
            • the covalent bond between two atoms are strong
              • There is a strong electrostatic attraction between the shared pair of electrons and the nuclei of the atoms involved, since the electrons are negatively charged and the nuclei are positively charged
            • Weak intermolecular forces exist between individual molecules
              • E.g. Each liquid water molecule consists of two hydrogen atoms covalently bonded to an oxygen atom, and in between two individual water molecules there are weak intermolecular forces
              • Simple molecular structures have covalent bonds joining the atoms together, but intermolecular forces that act between neighbouring molecules
            • Dot and cross diagram
          • hydrogen (H2), chlorine (Cl2), oxygen (O2), nitrogen (N2), hydrogen chloride (HCl), water (H2O), ammonia (NH3) and methane (CH4)
            • dot and cross diagram for these
          • They have low melting and boiling points as there are only weak intermolecular forces acting between the molecules
            • An increase in the relative molecular mass of a substance means that there are more electrons in the structure, so there are more intermolecular forces of attraction that need to be overcome when a substance changes state
            • So larger amounts of heat energy are needed to overcome these forces, causing the compound to have a higher melting and boiling point
          • giant covalent structure
            • Diamond
              • Diamond and graphite are  allotropes of carbon
                • Diamond has the following physical properties:It does not conduct electricityIt has a very high melting pointIt is extremely hard and has a density of 3.51 g / cm3
                • All the outer shell electrons in carbon are held in the four covalent bonds around each carbon atom, so there are no freely moving charged particles to the current
                  • he four covalent bonds are very strong and extend in a giant lattice, so a very large amount of heat energy is needed to break the lattice
                    • Diamond is used in jewellery and for coating blades in cutting tools
            • Graphite
              • Each carbon atom in graphite is bonded to three others forming layers of hexagons, leaving one free electron per carbon atom
                • These free electrons migrate along the layers and are free to move and carry charge, hence graphite can conduct electricity
                • weak intermolecular forces, so the layers can slide over each other making graphite soft and slippery
                  • Graphite has the following physical properties:It conducts electricity (delocalised electron) and heat. It has a very high melting pointIt is soft and slippery and less dense than diamond (2.25 g / cm3)
                    • It is used in pencils and as an industrial lubricant, in engines and in locks
            • fullerene
              • Fullerenes are a group of carbon allotropes which consist of molecules that form hollow tubes or spheres
                • They also have a huge surface area and are useful for trapping catalyst molecules onto their surfaces making them easily accessible to reactants so catalysis can take place
                  • useful for targeted drug delivery systems
              • In this fullerene, 60 carbon atoms are joined together forming 20 hexagons and 12 pentagons which produce a hollow sphere that is the exact shape of a soccer ball
    • ions are formed when atoms loose or gain elctrons
      • they do this to gain a full outer shell
        • the number of ions lost or gained is the same a the charge
      • positive ions are called cations
        • they form when they lose electrons.
      • negative charges ions are anions
        • they form when they gain electrons
      • All metals lose electrons to other atoms to become positively charged ions
      • All non-metals gain electrons from other atoms to become negatively charged ions
      • negative ions
      • Positive ions
    • METAL AND NON-METAL
      • formulae for ionic compounds
        • use swap and drop to work out the chemical formula
      • oppositely charged ions are strongly attracted to each other
        • Dot and cross diagram
      • it is the transfer of electrons from the outer shell of the metal to the outer shell of the non metal
        • the charges are held together by electrostatic attractions between oppositely charged ions
    • Ionic substances have high melting and boiling points due to the presence of strong electrostatic forces acting between the oppositely charged ions
      • These forces act in all directions and a lot of energy is required to overcome them
      • Ionic compounds are made of charged particles called ions which form a giant lattice structure
      • Ionic compounds can conduct electricity in the molten state or in solution as they have ions that can move and carry charge
        • They cannot conduct electricity in the solid state as the ions are in fixed positions within the lattice and are unable to move

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