Bonding

Description

A2 Chemistry (Physical 1) Mind Map on Bonding, created by Dominic Weston on 15/02/2018.
Dominic Weston
Mind Map by Dominic Weston, updated more than 1 year ago
Dominic Weston
Created by Dominic Weston about 6 years ago
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Resource summary

Bonding
  1. Ionic
    1. Structure
      1. Ionic crystals are giant lattices of ions
        1. "Giant" as made up of many repeating units
      2. Properties
        1. Conduct electricity when molten or dissolved
          1. Ions are free to move and carry a charge
          2. High melting points
            1. Strong electrostatic forces need lots of energy to break bonds
            2. Tend to dissolve in water
              1. Polar water molecules pull ions aways from lattice causing it to dissolve
            3. Bonding
              1. Strong electrostatic forces of attraction between oppositley charged ions
                1. Electrons transfered between one atom to another forming ions
                  1. Not just atons, compounds can form compound ions
                    1. Sulfate SO4 ^2-
                      1. Hydroxide OH-
                        1. Nitrate NO3 ^-
                          1. Carbonate CO3 ^2-
                            1. Ammonium NH4 ^+
                              1. Compounds have overall neutral charge
                      2. Covalent
                        1. Molecules held together by strong covalent bonds
                          1. Atoms share electrons to fully saturate both outer shells
                            1. Both nuclei attact to shared electrons electrostatically
                              1. Double or triple covalent bonds share multiple pairs or electrons
                                1. Covalent bonds shown by 'dash' e.g. C-H
                                  1. Covalent bonds don't break during melting or boiling, other than giant covalent substances
                                    1. To melt or boil, just overcome the intermolecular forces, dont need break covalent bonds
                                      1. Gives simple covalent compounds relatively low melting / boiling points
                                        1. So Cl2 is gas at room temp has low MP and BP
                                          1. Diamond does need the covalent bonds broken, sublimes at 3600 cel
                                          2. MP and BP determined by strength of attraction between particles
                                2. Dative covalent bond
                                  1. Covalent bond in which both electrons come from the same atom
                                    1. Shown by an arrow to replace the 'dash' N-->H
                              2. Giant Covalent structures (Macromolecular)
                                1. Many atoms covalently bonded
                                  1. Diamond
                                    1. Hardest known substance
                                      1. Made of carbon, each bonded covalently with 4 other carbon atoms
                                        1. Forms a tetrahedral shape with very strong covalent bonds
                                          1. High melting point, extremely hard, good thermal conductor
                                            1. Cannot conduct electricty (all e- held in bonds), cannot dissolve, refracts light
                                    2. Graphite
                                      1. Carbon arranged in sheets of flat hexagons with delocalised e-
                                        1. Weak bonds between layers causes them to slide in pencils
                                          1. Delocalised eletrons can move to carry a charge
                                            1. Layers far apart compared to covalent bonds - gives a low density makes strong and lightweight
                                              1. Strong covalent bonds in hexagon sheets causes high melting point
                                                1. Completely insoluble
                                        2. one carbon bonded to 3 others
                                    3. Shape of molecules
                                      1. Shape of a molecule depends on the number or pairs of electrons
                                        1. Electron pairs exist as charged clouds - there is a high probability of electron pair
                                          1. As the clouds are all negative they repel each other
                                            1. Shape affects how much it repels other clouds
                                              1. LP:LP strongest repulsion, biggest angles
                                                1. LP:BP Strong
                                                  1. BP:BP Weakest repulsion, smallest angles
                                                    1. Can work out the shape of molecule using VSEPR
                                                      1. Find number of electrons on the outer shell of central atom
                                                        1. Find how many electrons are used in bonding pairs
                                                          1. Check for charge - positive = less electrons
                                                            1. Sort any left over electrons as lone pairs
                                                        2. Shapes
                                                          1. 2 Pairs
                                                            1. 2 BP Linear
                                                            2. 3 Pairs
                                                              1. 3 BP Trigonal Planar
                                                              2. 4 Pairs
                                                                1. 4 BP Tetrahedral
                                                                  1. 3BP 1LP Trigonal Pyramidal
                                                                    1. 2BP 2LP Bent
                                                                    2. 5 Pairs
                                                                      1. 5 BP Trigonal Bipyramidal
                                                                        1. 4BP 1LP Seesaw
                                                                          1. 3BP 2LP T-shaped
                                                                          2. 6 Pairs
                                                                            1. 6 BP Octahedral
                                                                              1. 4BP 2LP Square Planar
                                                                2. Polarisation and Forces
                                                                  1. Intermolecular forces hold molecules together
                                                                    1. Electrogenativity is the ablility of an atom to attact an electron pair
                                                                      1. Fluorine, oxygen, chlorine all strongly electronegative
                                                                      2. These forces are very weak, weaker than covalent, ionic and metallic bonds
                                                                        1. vann der Waals
                                                                          1. Perm. Dipole-Dipole
                                                                            1. Hydrogen
                                                                              1. Only happens between FON elements when covalently bonded to hydrogen
                                                                                1. FON very electrogenative, draws BP electrons from H
                                                                                  1. As polar bond and Hydrogen high charge density, hydrogen can form bonds with lone pairs on FON atoms
                                                                                    1. Increases boiling, melting points. Water, HF higher boiling point in halides cause of h-bonds
                                                                              2. Polar Bonds
                                                                                1. Causing weak electrostatic fordes of attaction between partial charges
                                                                              3. Cause all atoms and molecules to attract to each other
                                                                                1. At any moment electrons likely to be on one side of the atom causing a temp. dipole
                                                                                  1. This can cause another temp. dipole opposite charged on the next atom, 2 dipoles attracted to each other
                                                                                    1. Temp. dipoles constantly created/destroyed overall attraction though
                                                                          2. Covalent bonds polarised by differences in electronegativity
                                                                            1. Covalent bonds between the same element are non-polar as same electronegativity
                                                                              1. Water is polar and substances that are polar will dissolved well in it
                                                                            2. Difference in electronegativity causes polar bond and a permanent dipole
                                                                              1. Dipole is a difference in charge between 2 by shift in electron density
                                                                            3. Metallic
                                                                              1. Metals exist in giant metallic lattice structures
                                                                                1. Outer most shell of electrons is delocalised
                                                                                  1. Leaving a positive metal ion that is attracted to d.electrons
                                                                                    1. Forms a lattice of closely packed positive ions
                                                                                      1. In a sea of delocalised electrons (metalic bonding)
                                                                                        1. Properties
                                                                                          1. High melting points as strong electrostatic attraction between electrons and ions
                                                                                            1. More delocalised electrons per atom, stronger bonding, so higher melting point
                                                                                              1. D.electrons can pass kinetic energy to each other making them good thermal conductors
                                                                                                1. Good electrical conductors as d.electrons can move to carry a current / charge
                                                                                                  1. Insoluble (except liquid metals)
                                                                                          2. Materials (NOT RELATED TO METALLIC)
                                                                                            1. Covalent bonds don't break during melting or boiling
                                                                                              1. To melt or boil, only break bond between molecules, inter force
                                                                                                1. Simple covalent, easy to overcome these forces
                                                                                                  1. Giant covalent need to break covalent bonds
                                                                                                    1. thats why it never really melts, only sublimes at 3600 cel
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