Chapter 6 -Shapes Of Molecules And Intermolecular forces

• What are the shapes of simple covalent molecules , a result of?


  They occur as a result of bonded groups of electrons around the central atom, repelling eachother and getting as far away from eachother as possible
• Describe how a Linear simple covalent molecule looks like? What is the bond angle .

  Linear- Bond angle 180 degrees

  A) Blank

  
• What is Electron Group Repulsion Theory?


  States that groups of electrons(either bonded pairs or lone pairs), around a central atom with their negetive charges , will repel eachother and move as far apart from eachother as they can to minimise the repulsion between them.
• How many electron groups are in the outer shell of the central atom in a linear covalent molecule?


  2
• How many number of electronss are there in the outer shell of the central atom in a trigonal planar?


  3
• How many number of electronss are there in the outer shell of the central atom in Tetrahedral ?

  4
• How many number of electronss are there in the outer shell of the central atom in an Octahedral?


  6
• Why is an octahedral , not callled a hexahedral , when it only has that many electronss in the outer shell of the central atom?


  It has eight faces in 3D form
• What are the bond angles in a trigonal planar ,and describe its shape?


  120 degrees

  
• What does VESPR /VSEPR stand for , what is its summerised name ?

  
  

  
  

  1.VESPR/VSEPR stands for Valence Shell Electron Pair Repulsion theory.

  
  

  2.Its summarized name is VSEPR theory/Electron group repulsion theory.

  
  

  • Electron pairs repel each other whether they are in bonding pairs or lone pairs.
  • Valence electron pairs are oriented to be as far apart as possible to minimize repulsions.
• Why do lone pairss have more repulsion than bonding pairs?


  Lone pairs have more repulsion that bonding pairs ,because they are more electron dense, therefore , more negetivity to repel bonding pairs with less negetivity
• Describe the shape of a tetrahedral , and what is its bond angle?


  Bond angle: 109.5 degrees

  
• How many number of electrons are there in the outer shell of the central atom in a triagnol bipyrimidal ?

  5
• Describe the shape of a octahedral and state its bond angles

  It has bond angles of 90 degrees

  
• Describe the shape of a triagonal bipyrimidal , and state the three angles present.


  120,90and 180 degrees

  
• Why do the electrons follow the Electron Repulsion theory?


  To minimise repulsion and become more stable
• What is the formula for calculating lone pairs?


  Lone pairs = Total valence electrons - 8(n) / 2

  n=The number of atoms around the central atom
• What do the wedges and dashed lines represent in a molecule?

  Wedged lines= Atom is coming out of the page towards you

  Dashed lines= Going into the page , away from you

  Just helps you to visually imagine the different planes and make diagrams clearer
• Whats an example of a octahedral?


  SF6 - sulfur hexafluride
• By how much do lone pairs reduce the bond angles in a molecule by?


  2.5 degrees
• State the ascending order of magnitude of strength between bonded pair / bonded pair , Lone pair/lone pair and Lone pair/bonded pair.


  1.Lone/Lone

  2.Lone pair/bonded Pair

  3. Bonded/Bonded
• When referring to the shape taken up by the electron groups , we include the _____ pairs and act as if they were _____ pairs . However when we are talking about the shape of the molecule itself , we ignore the lone pairs and refer to the shape ,made by the ____ pairs

  1.Lone pairs

  2.Bonded

  3.bonded
• What is the shape taken up by the molecule below?

  What is the shape taken up by the bonded pairs ?

  (It has one lone pair ,and three bonded pairs)


  For example - Ammonia

  A)

  B)

  
• 1.What is the shape taken up by the molecule?

  2.What is the shape taken up by the bonded pairs?

  ( the molecule has one lone pair and , two bonded pairs)

  1. Non-Linear
  2. Triagonal planar

  Example - Sulfur dioxide , Germanium dichloride
• 1.What is the shape taken up by the molecule?

  2.What is the shape taken up by the bonded pairs?

  ( the molecule has two lone pairs and , two bonded pairs)

  1.Non-Linear

  2. Tetrahedral

  For example - Water ,Sulfur dichloride
• No matter the type of covalent bond (whether dative ,single ,triple ect), they are all bonded within one particular region , so count as ONE bonded group /group.
• What is another name for triagonal bipyrimidal that has one lone pair?

  See-Saw
• What are the bond angles of a non-linear molecule with only ONE LONE PAIR?


  117.5 degrees
• What is the bond angle of a pyrimidal molecule?


  107 degrees
• What is the name of a triagonal bipyrimidal with TWO LONE PAIRS?


  T- shape
• What is the name of an octahedral with one lone pair?


  Square pyrimidal

  
• What is the name of an octahedral with two lone pairs?


  Square planar

  
• What is the method for determining the shape of a molecule?

  1.Draw out lewis structure/dot and cross

  2.Count the total number of electron groups and identify that shape

  3.Take into account the number of lone pairs and take into account the shape of the bonding pairs/shapes of atoms to determine the shape of the molecule
• Why do lone pairs have more repulsionthan bonded bonded pairs?


  They are more electron dense
• Why does a triagonal planar have bond angles of 109.5?


  Triagonal planar has 109.5 degreess between the bond angles because, they only have bonded pair bonded pair interactions which have weaker overal repulsion compared to if they were lone pair lone pair interactions or bonded pair lone pair interactions.
• Why are the noble gases not part of the Pauling electronegativity values?


  They tend not to form compounds
• What four elements have high electronegativity values?

  Flourine - 4.0

  Oxygen - 3.5

  Nitrogen - 3.0

  Chlorine- 3.0
• Whcih group in the periodic table have the lowest electronegativity values?


  Group One
• What is electronegativity?

  Electronegativity is the measure of an atom's ability to attract a pair of electrons in a covalent bond.
• What happens if the electronegativity in a covalant compound is quite large?


  One bonded atom will have a much greater attraction for the shared pair of electrons than the bonded atom with a lower electronegativity