1.4 Bonding

• What is an ionic bond?

  An electrical attraction between positive and negative ions and are formed between metals and non-metals.
• What diagram is used to show bonding in compounds?

  Dot and cross diagram. They show electrons in the outer shell.
• What happens in a covalent bond?

  A pair of electrons with opposite spins are shared between two atoms, with each atom giving one electron.
• What is coordinate bonding?

  A special type of covalent bond where both electrons come from one atom.
• What are the attractive and repulsive forces in bonded structures?

  Attractive forces:

  • Electron pairs attracted to nucleus in atom.
  • Magnetic force between electrons in a pair (spin).
  • Repulsive forces: Electrons in a pair repel each other.
  • Protons in each nucleus repel.
  • Pairs of electrons repel other pairs.
• What does all bonding result from?

  Electrical attraction and repulsion between protons and electrons with attractions greater than repulsion.
• What does an electron cloud show?

  Electron density distribution.
• What does ΔEN=0 mean?

  Pure covalent bond.
• What is electronegativity?

  The ability of an atom to attract electrons in a covalent compound. Its 'pulling power'.
• What does ΔEN=0↔2.1 mean?

  Polar covalent bond.
• What does ΔEN>2.1 mean?

  Pure ionic bond.
• What is the trend of electronegativties?

  Increases up a group and across a period
• How is a dipole created?

  It's created due to the difference in charge across a particle.
• What symbol do you use to show forces of attraction?

  H-Cl |||||||| H-Cl
• What is the name of the weak force of attraction?

  Van der Waals force.
• What are Van der Waals forces?

  At any given time one part of a molecule might be slightly more positive and one part slightly more negative. These tiny charges influence neighboring molecules, inducing the opposite charge in them and creating tiny forces of attraction between molecules. We form instantaneous dipoles or temporary dipoles often called van der Waals forces. The more electrons it has the more Van der Waals' forces that can be induced.
• What is the hydrogen bond?

  The hydrogen bond is a relatively strong intermolecular bond having a hydrogen atom joined to a highly electronegative element in a molecule, and bonding to another electronegative element in another molecule.
• What are the typically highly electronegative atoms?

  Fluorine, oxygen or nitrogen.
• What is intermolecular bonding?

  Intermolecular bonding takes place between molecules and governs physical properties like boiling temperatures.
• How can dipole interactions sometimes affect chemicals?

  Can causes boiling points to increase and makes them more soluble.
• What is electron pair repulsion theory?

  Groups of electrons around an atom (i.e. a pair of electrons in the same orbital) will repel each other and take up positions as far apart as possible. The repulsion between electron pairs are minimised in this way.
• What does VSEPR stand for?

  Valence Shell Electron Pair Repulsion.
• What is a bonding pair?

  A pair of shared electrons that make up a covalent bond.
• What is a lone pair?

  A pair of electrons that do not make up a bond.
• Linear molecule

  2 atoms around a central atom, 180°

  
• Trigonal planar molecule

  3 atoms around a central atom, 120°

  
• Tetrahedral molecule

  has to be drawn in a 3D plane, 4 atoms around a central atom, 109.5°

  
• Trigonal bipyramid molecule

  has to be drawn in a 3D plane, 5 atoms around a central molecule, 90° and 120°

  
• Octahedral molecule

  had to be drawn in a 3D plane, 6 atoms around a central atom, 90°

  
• What may the positions of electrons be influenced by?

  • A shared pair forming a single bond
  • A set of four in a double bond
  • An unshared pair (a lone pair).
• Summary of the force of repulsion.

  Lone pair - Lone pair (Strongest repulsion)

  Lone pair - Bonding pair

  Bonding pair - Bonding pair (Weakest repulsion)
• What is the shape of the water molecule?

  Bent or angular. Oxygen has 2 lone pairs (LP) and 2 bonding pairs (BP), therefore you would expect it to be tetrahedral. However, due to the LP-LP repulsion being stronger than the BP-BP the two hydrogen atoms are pushed down slightly.
• What are the steps to predict the shapes of molecules and ions?

  1. Draw a dot and cross diagram. List numbers of bonding pairs and lone pairs.
  2. Suggest a VSEPR shape.
  3. Sketch the molecule showing bonds and lone pairs.
  4. Apply the sequence for forces of repulsion to fully understand any distortion in the structure.
• What is it called when a bonded atom have a overfull outer shell?

  Expanded outer shell.
• What is it called when a bonded atom doesn't have a full outer shell?

  Electron deficient.