Chemistry - Bonding Structure & Properties of matter

Chemistry - Bonding Structure & Properties of matter

1. STRONG Chemical bonds

   • IONIC BONDING
     • Occurs in compounds formed between METAL & NON- METALS
     • Particles produced are oppositely charged ions
     • Only electrons in outer shell of METAL are TRANSFERRED
       • Metals - LOSE ELECTRONS - become +ly charged ions/ non metals GAIN ELECTRONS- become -ly charged ions
     • Ions produced by group 1+ 2 metals - and group 6+7 non metals - has electronic structure of NOBLE GAS ( group 0 - full outer shell)
   • METALLIC BONDING
     • Occurs in metallic ELEMENTS & ALLOYS
     • Atoms have DELOCALISED electrons
       • FOUND ON THE OUTER SHELL- delocalised electrons are free to move through WHOLE STRUCTURE
     • Metals are giant atomic structures arranged in a REGULAR pattern
   • COVALENT BONDING
     • Atoms SHARE PAIRS of electrons- covalent bonds are STRONG
     • Occurs in NON metallic elements and compounds of NON elements
     • Covalent bonded structures - either small molecule, polymers ( large molecules) or giant covalent structures ( i.e diamond/silicon dioxide)

2. PROPERTIES OF SUBSTANCES

   • Limitations of particle theory-/ simple model - NO FORCES / all particles are shown as SOLID SPHERE
   • STATES SYMBOLS - (s) - solid / (l) liquid / (g) gas/ (aq) aqueous solution - where the solvent is water
   • PROPERTIES OF IONIC COMPOUNDS
     • Ionic compounds = regular structures/ lattices -have strong electrostatic forces of attraction- in all directions = HIGH BPT + MPT- lots of energy needed to break many strong bonds
     • Ionic compounds CAN CONDUCT ELECTRICITY when melted or dissolved in water- IONS MOVE & CHARGE CAN FLOW
   • PROPERTIES OF ALLOYS & METALS
     • Pure metals = are ARRANGED IN LAYERS- so can be BENT/ SHAPED
     • But PURE METALS - too soft for many uses - so are mixed with OTHER metals - to make HARDER ALLOYS
     • Alloys have a DISORDERLY ARRANGEMENT due to different size of atoms
     • METALS AS CONDUCTORS
       • Metals - good electrical conductors - delocalised electrons can carry electric charge through metal
       • Metals = good thermal conductors- energy transferred via delocalised electrons
     • Most metals - have HIGH BPT + MPT - due to srong metallic bonds
   • PROPERTIES OF GIANT COVALENT STRUCTURES
     • Giant covalent structures = SOLIDS w/ VERY HIGH MPT
     • Atoms are joined by strong covalent bonds - that need to be overcome to melt/boil substances- i.e carbon allotropes ( silica/diamond)
   • PROPERTIES OF POLYMERS
     • Polymers - have v. LARGE molecules- the I.M.F( INTERMOLECULAR FORCES) between polymers are STRONG so substances are SOLID at room temp
     • Atoms in polymers - linked to other atoms via STRONG COVALENT BONDS
   • PROPERTIES OF SMALL MOLECULES
     • Substamces made up of SMALL molecules - usually GASES/LIQUIDS- low MPT +BPT
     • Only have week I.M.F forces in between molecules- these IMF and not covalent bonds are broken when substance melt/boils.
     • Note : IMF increases with SIZE of molecules - larger molecules = higher mpt + bpt
     • DON'T conduct ELECTRICITY -molecules don't have overall charge

3. IONIC COMPOUNDS

   • Ionic compound = GIANT structure of ions ( shows IONIC bonding)
   • Held together via Strong ELECTROSTATIC FORCES OF ATTRACTION between oppositely charged ions
   • Electrostatic forces - act is ALL directions -forming a LATTICE
   • EMPIRICAL FORMULA
     • EXAMPLE- Mg- 2e / Cl+2e - gives the empirical formula of MgCl2

4. CARBON STRUCTURES/ ALLOTROPES

   • DIAMOND - each carbon atoms forms 4 COVALENT BONDS with other carbon atoms - giant covalent structure- Diamond is VERY HARD/ HIGH MPT/ DOESN'T CONDUCT ELECTRICITY
   • GRAPHITE - carbon atom form 3 COVALENT bonds w/ 3 other carbon atoms- form HEXAGONAL rings - NO COVELENT BONDS BETWEEN LAYERS
     • Graphite - has 1 DELOCALISED ELECTRON from each carbon atom - so a similar to metals in this way
   • GRAPHENE - single layer of graphite- used in electronics/composites
     • FULLERENES
       • Fullerenes are molecules of carbon atoms w/ HOLLOW SHAPES- are made from hexagonal rings of carbona toms - may contain ring with 5 or 7 carbon atoms too - i.e Buckminister Fullerene (C60)- it is a sphere
       • CARBON NANOTUBES
         • ARE CYLINDRICAL fullerenes - have a HIGH length to diameter ratio - properties make them USEFUL for nanotechology/materials/electronics/cosmetics/catalysts
           • (NANO PARTICLES) Approx.1-100nm in diameter- so have higher SA:VOL ratio - smaller quantities are needed for it to be effective than normal size particles

5. LIMITATIONS OF DOT + CROSS/ BALL AND STICK DIAGRAMS

   • Ball + stick - pros - shows charges on ions/ numer of atoms / 3D arrangement/ cons - ions are closer together/ false image of bond direction
   • Melting & freezing happen at mpt / boiling and condensing happen at bpt

6. 3 STATES OF MATTER

   • The energy required to change states - depends on strength of forces between particles and type of bonding/strucutrw - stronger bonging/forces = higher bpt & mpt

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