1.4 Bonding

• What is ionic bonding ?


  When one atom donates one or more electrons to another atom for a full outer shell.
• What are atoms that gain electrons called ?


  Anion (negative ion)
• What is an atom that loses electrons called ?


  Cation (Positive ion)
• Why are ionic bonds strong ?


  Electrostatic attraction (Strong attraction between the negative and positive ions)
• Why do ionic bonds have a high melting and boiling points ?


  Due to the strong bonds, a lot of energy is required to break them.
• How are ionic lattices formed ?


  The strong attraction between the ions lead to the formation
• How are ions in an ionic lattice arranged ? 


  Arranged so each anion is surrounded by a certain number of cations (and vice versa)

  
• Why are ions arranged in a certain way in an ionic lattice ?

  To maximise attraction between ions and minimise repulsion between ions.
• What are ionic bonding between ?


  Non metals and metals
• What is Covalent Bonding ?

  Where atoms give one electron to the shared pair of electron

  
• Coordinative / dative bonding

  It is a covalent bond where both electrons in a bond come from the same atom

  
• Electronegativity 


  Measure of the electron attracting power of an atom in a covalent bond
• Electronegativity trends 


  Increases across and up the periodic table
• The more electronegative atom will have a greater share of the electrons in a bond

  
• Intermolecular forces are those that occur between molecules
• Intramolecular forces are those that occur within molecules
• Three main types of intermolecular forces

  • Temporary dipole-dipole
  • Permanent dipole-dipole
  • Hydrogen bonds
• Temporary dipole-dipole


  A type of intermolecular force between neighbouring non - polar molecules and is weak due to temporary dipole moments. E.g between iodine molecules in iodine crystal (van der Waals)
• Why does temporary dipole-dipole forces not last ?

  Fluctuating (changing) electron distribution.
• Temporary dipole-dipole charges

  As the electrons orbit the atoms they will be on one side at a time making that side partially negative and the other side will become partially positive
• Induced dipole 


  The delta negative on the molecules repels the electrons in adjacent molecules causing (inducing) a dipole

  
• Size of atom and van der waals 


  Size of atom increases = strength of van der waals increase.

  Because the outer electrons are further away from the nucleus
• Permanent Dipole-Dipole Force


  A type of intermolecular force that occurs between two permanent dipoles, caused by the attraction between similarly charged ends of two molecules. E.g found between HCL molecules in hydrogen chloride (van der Waals)
• What is ionic bonding?

  One atom donates electrons to another
• What is a cation?

  Atom that loses electrons
• What is an anion?

  Atom that gains electrons
• Why are ionic bonds strong?

  Due to strong attraction between opposite charges
• What leads to high melting and boiling points in ionic compounds?

  Strong attraction between ions
• What is an ionic lattice?

  Formation of an ionic solid
• What is covalent bonding?

  Atoms share one or more electrons
• What is co-ordinate (dative) bonding?

  Both electrons in a bond come from one atom
• What is hydrogen bonding?

  Strongest intermolecular force involving hydrogen
• When does hydrogen bonding occur?

  When hydrogen is bonded to N, O, or F
• What is electronegativity?

  Measure of electron attracting power of an atom
• What characterizes a non-polar covalent bond?

  Equal sharing of electrons between atoms
• What characterizes a polar covalent bond?

  Unequal sharing of electrons between atoms
• What happens to electron sharing in co-ordinate bonds?

  One atom donates both electrons in the bond
• What defines a polar molecule?

  Molecule with an unbalanced charge distribution
• How is polarity in bonds determined?

  By the electronegativity of the atoms
• What are intermolecular forces?

  Forces that occur between molecules