CHEMICAL BONDING

Anmerkungen:

• Intermolecular forces are forces of attraction or repulsion which act between neighboring particles (atoms, molecules, or ions).
• Stronger than intermolecular forces

1. IONIC BONDING

   Anmerkungen:

   • Ionic bonding is a type of chemical bond that involves the electrostatic attraction between oppositely charged ions, and is the primary interaction occurring in ionic compounds. 
   • Transfer of electrons between a metal + non-metal
   1. PHYSICAL PROPERTIES
      1. HIGH MELTING & BOILING POINT

         Anmerkungen:

         • High temperatures are required to overcome the attraction between the positive and negative ions in ionic compounds. Therefore, a lot of energy is required to melt ionic compounds or cause them to boil.
         1. LARGE AMOUNT OF ENERGY NEEDED TO BREAK BONDS
         2. HIGHER ENTHALPIES OF FUSION & VAPORIZATION

            Anmerkungen:

            • They usually have enthalpies of fusion and vaporization that may be 10 to 100 times higher than those of most molecular compounds.
            •  The enthalpy of fusion is the heat required melt a single mole of a solid under constant pressure.
            •  The enthalpy of vaporization is the heat required for vaporize one mole of a liquid compound under constant pressure.
      2. LATTICE STRUCTURE

         Anmerkungen:

         • Ionic compounds form crystal lattices rather than amorphous solids.
      3. HARD

         Anmerkungen:

         • Ionic crystals are hard because the positive and negative ions are strongly attracted to each other and difficult to separate. 
         • However, when pressure is applied to an ionic crystal then ions of like charge may be forced closer to each other.
      4. BRITTLE

         Anmerkungen:

         • The electrostatic repulsion can be enough to split the crystal, which is why ionic solids also are brittle.
      5. CONDUCTS ELECTRICITY
         1. WHEN DISSOLVED IN WATER (AQUEOUS)

            Anmerkungen:

            • Dissociated ions are free to conduct electric charge through the solution.
         2. MOLTEN STATE

            Anmerkungen:

            • Molten ionic compounds (molten salts) also conduct electricity.
      6. SOLUBLE IN WATER (POLAR)

         Anmerkungen:

         • Liquids and ions are attracted to each other.
   2. ANION (NON-METALS)
      1. ATOMS GAIN ELECTRONS
      2. FORMS NEGATIVE IONS
   3. CATION (METALS)
      1. ATOMS LOSE ELECTRONS
      2. FORMS POSITIVE IONS
2. COVALENT BONDING

   Anmerkungen:

   • A covalent bond is formed between non metal atoms, which combine together by sharing electrons. .
   • Covalent compounds have no free electrons and no ions so they don't conduct electricity
   1. POLAR COVALENT BONDING
      1. UNEVEN SHARING OF ELECTRONS

         Anmerkungen:

         • In a polar covalent bond, the electrons are not equally shared because one atom spends more time with the electrons than the other atom.
      2. PARTIAL POSITIVE AND PARTIAL NEGATIVE ENDS
      3. ELECTRONEGATIVITY VALUES MUST BE 0.4 OR GREATER
      4. STRONGER INTERMOLECULAR FORCES THAN NORMAL COVALENT BONDS
   2. SIMPLE MOLECULES

      Anmerkungen:

      • These contain only a few atoms held together by strong covalent bonds. 
      1. CO2, H20, CH4, ETC.
      2. PROPERTIES
         1. LOW MELTING & BOILING POINTS

            Anmerkungen:

            • Weak Van der Waals forces between molecules. 
         2. NON-CONDUCTIVE

            Anmerkungen:

            • Substances with a simple molecular structure do notconduct electricity. This is because they do not have any free electrons or an overall electric charge.
   3. GIANT STRCUTURES

      Anmerkungen:

      • Giant covalent structures contain a lot of non-metal atoms, each joined to adjacent atoms by covalent bonds.
      1. LATTICE STRUCTURES

         Anmerkungen:

         • The atoms are usually arranged into giant regular lattices - extremely strong structures because of the many bonds involved. 
      2. ALLOTROPES

         Anmerkungen:

         • Allotropes are different structural modifications of an element; the atoms of the element are bonded together in a different manner.
         1. GRAPHITE

            Anmerkungen:

            • Each carbon atom in a layer is joined to only three other carbon atoms.
            1. FORM LAYERS

               Anmerkungen:

               • Graphite is a form of carbon in which the carbon atoms form layers. These layers can slide over each other.
            2. USED AS PENCILS AND LUBRICANT

               Anmerkungen:

               • The slidable layers make graphite so much softer.
            3. CONDUCTS ELETRICITY
         2. DIAMOND

            Anmerkungen:

            • Diamond is a form of carbon in which each carbon atom is joined to four other carbon atoms, forming a giant covalent structure.
            1. VERY HARD
            2. HIGH MELTING POINT
            3. DOESN'T CONDUCT ELECTRICITY
         3. SILICA

            Anmerkungen:

            • Structure similar to diamond, but contains silicon and oxygen atoms, instead of carbon atoms.
            1. FOUND IN SAND
            2. VERY HARD
            3. HIGH MELTING POINT
         4. BUCKMINSTERFULLERENE

            Anmerkungen:

            • It is actually not a giant covalent structure, but a giant molecule 
            1. FORM HEXAGONS/PENTAGONS
            2. USED IN LUBRICANTS
3. METALLIC BONDING

   Anmerkungen:

   • Metallic bonding is the type of bonding found in metallic elements. This is the electrostatic force of attraction between positively charged ions and delocalised outer electrons.
   1. ELECTRONS ARE DELOCALIZED
   2. STRONG ATTRACTIVE FORCES IN THE BOND
   3. PROPERTIES

      Anmerkungen:

      • These bonds result in physical properties of strength, malleability, ductility, and conduction.
      1. MALLEABLE & DUCTILE

         Anmerkungen:

         • Layers of ions slide over each other. 
      2. CONDUCTS HEAT AND ELECTRICITY

         Anmerkungen:

         • There are free electrons to carry a charge. 
      3. HIGH MELTING & BOILING POINT
      4. INSOLUBLE IN WATER
   4. WITHIN A METAL
   5. RELATE USES OF METAL TO PROPERTIES
      1. Fe
         1. BRIDGES/STRUCTURES
      2. Cu
         1. ELECTRICAL WIRING
         2. PLUMBING
         3. BRASS
         4. COINAGE
      3. Al
         1. OVERHEAD WIRING
         2. ALLOYS FOR AIRCRAFT
      4. Mg
         1. FLARES
         2. HIGH STRENGTH FOR ALLOYS FOR AIRCRAFT

Anmerkungen:

• An intramolecular force is any force that holds together the atoms making up a molecule or compound.
• Weaker than intramolecular forces

1. HYDROGEN BONDS

   Anmerkungen:

   • A hydrogen bond is a special type of dipole-dipole attraction which occurs when a hydrogen atom bonded to a strongly electronegative atom exists in the vicinity of another electronegative atom with a lone pair of electrons.
   1. STRONGEST OUT OF THE 3 FORCES

      Anmerkungen:

      • Takes more energy to break the bonds
   2. IE. WATER
      1. COMPOSED OF 2 HYDROGENS & 1 OXYGEN

         Anmerkungen:

         • Because oxygen has two lone pairs, two different hydrogen bonds can be made to each oxygen
         1. OXYGENS SLIGHTLY NEGATIVE
         2. HYDROGEN SLIGHTLY POSITIVE
      2. POLAR
   3. ATTACHED TO ONE OF THE MOST ELECTRONEGTIVE ELEMENTS (N,O,F)

      Anmerkungen:

      • The three elements listed  will grab the electrons for itself, and leave the hydrogen atom with virtually no electron density (since it had only the one). 
      • Now, if another molecule comes along with a lone pair, the hydrogen will try to position itself near that lone pair in order to get some electron density back.
      1. HYDROGEN ACQUIRE POSITIVE CHARGE
      2. AT LEAST ONE LONE PAIR
   4. OCCUR IN BOTH INORGANIC AND ORGANIC MOLECULES
   5. HIGH BOILING AND MELTING POINT

      Anmerkungen:

      • They require more energy to break the bonds.
   6. PLAY A KEY ROLE IN DETERMINING THE PROPERTIES OF WATER
   7. PLAY A ROLE IN DETERMINING THE PROPERTIES IN PROTEINS.
2. VAN DER WAALS FORCES

   Anmerkungen:

   • Van der Waals forces are driven by induced electrical interactions between two or more atoms or molecules that are very close to each other.
   1. DIPOLE-DIPOLE FORCES

      Anmerkungen:

      • Dipole-dipole forces are attractive forces between the positive end of one polar molecule and the negative end of another polar molecule. 
      1. HAVE POSITIVE AND NEGATIVE REGIONS

         Anmerkungen:

         • Some elements have more affinity for the electrons than others, and they hang out around that atom more. 
      2. STRONGER THAN DISPERSION FORCES
         1. 5KJ - 20KJ
      3. POLAR

         Anmerkungen:

         • Slightly positive and slightly negative
      4. IE. ICI, SCI2, PCI3.
      5. POSITIVE END ATTRACTS NEGATIVE END
      6. MOLECULES NEED TO BE VERY CLOSE
         1. LIKE AS IF THEY WERE LIQUID
         2. TOUCHING OR ALMOST TOUCHING
   2. LONDON DISPERSION FORCES (LDF)

      Anmerkungen:

      • The London dispersion force is a temporary attractive force that results when the electrons in two adjacent atoms occupy positions that make the atoms form temporary dipoles.
      1. FOUND IN ALL MOLECULES (POLAR&NON-POLAR)
      2. WEAKEST INTERMOLECULAR FORCE
         1. LOWER BOILING AND MELTING POINT

            Anmerkungen:

            • Bonds need less energy to break
      3. STRONGER BETWEEN MOLECULES THAT ARE EASILY POLARIZED
      4. WEAKER BETWEEN MOLECULES THAT ARE NOT EASILY POLARIZED