bonding

• ionic bonding is electrostatic forces of attraction between oppositely charged ions formed by electron transfer
• metals atoms lose electrons to form positive ions and non-metals atoms gain electrons to form negative ions
• ionic bonding is stronger and the melting points are higher when the ions are smaller and/or have higher charges
• positive ions are smaller compared to their atoms because it has one less shell of electrons

  the ratio of protons to electrons increases so there is a greater net force on remaining electrons holding them more close
• negative ions are larger than their corresponding atoms as they have more electrons but the same number of protons

  the pull of the nucleus is shared over more electrons, making the attraction per electron less so the ion is bigger
• ionic radii increases going down the group as the ions have more shells of electrons
• covalent bond is a shared pair of electrons
• dative covalent bond forms when shared pair of electrons in the covalent bond come from only one of the bonding atoms

  sometimes called co-ordinate bond
• in dative covalent bonding, the direction of the arrow goes from the atom providing the lone pair to the atom that is deficient
• metallic bonding is the electrostatic force of attraction between positive metal ions and delocalised electrons
• factors that affect strength of metallic bonding

  1. number of protons/strength of nuclear attraction
  2. number of delocalised electrons (outer shell electrons) per atom
  3. size of ion
• more protons means stronger metallic bonding
• more delocalised electrons means stronger metallic bonding
• smaller ion means strong metallic bonding
• structure of ionic compound is ionic lattice
• structure of covalent can be simple molecule or macromolecule
• metals are arranged in giant metallic lattice structure
• ionic compounds have high melting points because of giant ionic lattice with strong electrostatic forces of attraction between oppositely charged ions
• ionic compounds have generally good solubility in water
• ionic compounds have poor conductivity when solid as ions cannot move as they are fixed in lattice
• ionic compounds can conduct well when molten as ions can move
• simple molecules have low melting and boiling points due to there being weak intermolecular forces between molecules
• simple molecules have generally poor solubility in water
• simple molecules have poor conductivity when solid and molten as there are no ions to conduct and electrons are localised (fixed in place)
• simple molecules are mostly gases and liquids
• ionic compounds are generally crystalline solids
• macromolecules have a high melting and boiling point as they have many strong covalent bonds which require a lot of energy to overcome
• macromolecules are insoluble in water
• macromolecules like diamond and sand have poor conductivity when solid as electrons cannot move

  graphite has good conductivity when solid as there are free delocalised electrons between layers
• macromolecules have poor solubility when molten
• macromolecules are generally solids
• metals have high boiling and melting points are there are strong electro static forces of attraction between positive ions and sea of delocalised electrons
• metals are insoluble in water
• metals have good conductivity when molten and solid as there are delocalised electrons that can move through the structure
• metals are malleable as positive ions in the lattice are identical and planes of ions can slide easily over one another
• linear molecules

  two bond pairs and zero lone pairs

  bond angle of 180

  
• trigonal planar

  3 bond pairs 0 lone pairs

  bond angle 120

  
• tetrahedral

  4 bond pairs 0 lone pairs

  bond angle 109.5

  
• trigonal pyramidal

  3 bond pairs 1 lone pair

  bond angle 107

  
• bent

  2 bond pairs 2 lone pairs

  bond angle 104.5