6 Shapes of Molecules and Intermolecular Forces Flashcards
Does a lone pair or bonded pair repel more strongly? (1 mark)
Lone pair
Why does a lone pair repel more strongly than a bonded pair? 2 marks)
A lone pair is slightly closer to the central atom, and occupies more space.
What is the bond angle decreased by for each lone pair? (1 mark)
2.5 degrees
What is the bond angle and shape of methane? (2 marks)
Tetrahedral
109.5
What is the bond angle of a tetrahedral molecule? (1 mark)
109.5
What is the shape of a molecule with bond angle 109.5?
Tetrahedral
What is the shape and bond angle of a molecule with 4 bonded pairs and no lone pairs? (2 marks)
Tetrahedral 109.5
What is the shape and bond angle of ammonia? (2 marks)
Pyramidal
107
What is the bond angle of a molecule with a pyramidal shape? (1 mark)
107
What is the shape of a molecule with bond angle 107? (1 mark)
Pyramidal
What is the shape and bond angle of a molecule with 2 bonded pairs and 2 lone pairs? (2 marks)
Non- linear
104.5
What is the shape of a molecule with bond angle 104.5? (1 mark)
Non-linear
What is the shape and bond angle of a molecule with three bonded paired and one lone pair? (2 marks)
Pyramidal
107
What is the bond angle of a molecule with a non-linear shape? (1 mark)
104.5
What is the shape and bond angle of water? (2 marks)
Non-linear
104.5
What is the shape of a molecule with 2 electron regions? (2 marks)
Linear
What is the bond angle of a linear molecule? (1 mark)
180
What is the bond angle and shape of carbon dioxide? (2 marks)
Linear
180
What is the shape of a molecule with bond angle 180? (1 mark)
Linear
What is the shape and bond angle of a molecule with 3 electron pairs/regions?
Trigonal planar
120
What is the shape of a molecule with bond angle 120? (1 mark)
Trigonal planar
What is the shape and bond angle of BF3? (2 marks)
Trigonal planar
120
What is the bond angle of a molecule with a trigonal planar shape? (1 mark)
120
What is the bond angle and shape of sulphur hexafluoride? (2 marks)
Octahedral
90
What is the bond angle of a molecule with an octahedral shape? (1 mark)
90
What is the bond angle and shape of a molecule with 6 electron pairs/regions? (2 marks)
90
Octahedral
What is the shape of a molecule with bond angle 90? (1 mark)
Octahedral
What is electronegativity? (1 mark)
The attraction of a bonded atom for the pair of electrons in a covalent bond.
How is electronegativity measured? (1 mark)
The Pauling scale
Describe electronegative on the periodic table. (2 marks)
The top right of the periodic table contains the most electronegative elements. With Florine being in the corner (ignore group 0).
Is an ionic or covalent bond more electronegative? (1 mark)
Ionic
What is the electronegativity difference of a covalent bond? (1 mark)
0
What is the electronegativity difference of a polar covalent bond? (1 mark)
0 to 1.8
What is the electronegativity difference of an ionic bond? (1 mark)
Greater than 1.8
What does a bond being non-polar mean? (1 mark)
The bonded electron pair is shared equally between the bonded atoms.
What does it mean when a bond is described as polar? (1 mark)
The bonded electron pair is shared unequally between the bonded atoms.
Why is carbon dioxide non-polar even though it contains two C=O bonds with permanent dipoles? (1 mark)
The two dipoles act I’m opposite directions and exactly oppose each other (due to a linear shape).
What are the three main catagories of intermolecular forces? (3 marks)
Induced dipole-dipole interactions
Permanent dipole-dipole interactions
Hydrogen bonding
Which intermolecular force is the strongest? (1 mark)
Hydrogen bond
Which intermolecular bond is the weakest? (1 mark)
Induced dipole-dipole interactions
Where are induced dipole-dipole interactions? (2 marks)
Exist between all molecules.
They act between induced dipoles in different molecules.
Describe the origin of induced dipole-dipole interactions. (3 marks)
Movement of electrons produces a changing dipole in a molecule.
At any instant, an instantaneous dipole will exist (position is alway shifting).
This instantaneous dipole induces a dipole on a neighbouring molecule.
Etc.
Describe the strength of the induced dipole-dipole interactions in a molecule with more electrons. (3 marks)
Larger instantaneous and induced dipoles
Greater the induced dipole-dipole interactions
The stronger the attractive forces between molecules.
What are permanent dipole-dipole interactions? (2 marks)
They act between the permanent dipoles in different polar molecules.
Describe the bonding and intermolecular forces in a simple molecular lattice. (2 marks)
Strong covalent bonds
Weak intermolecular forces.
What happened when a simple non-polar molecular substance is added to a non-polar solvent? (3 marks)
Intermolecular forces form between the molecules and the solvent.
The interactions weaken the intermolecular forces in the simple molecular lattice.
The intermolecular forces break.
The compound dissolves.
Why are non-polar simple molecular substances insoluble in polar solvents? (2 marks)
The intermolecular bonding within the polar solvent is too strong to be broken, so there is little interaction between the molecules keep s in the lattice and the solevent molecules.
What is the solubility of a polar simple molecular substance dependent on? (1 mark)
The strength of the dipole.
Describe the electrical conductivity of simple molecular structures. (2 marks)
There are no mobile charge carriers, so they do not conduct electricity.
What three elements can form a hydrogen bond with H? (3 marks)
Oxygen
Nitrogen
Fluorine
Why is ice less dense than water? (2 marks)
Hydrogen bonds hold water molecules apart in an open lattice structure in ice.
Why does water have a relatively high melting and boiling point? (2 marks)
Hydrogen bonds are really strong, require more energy to be broken.
What is the bond angle of a molecule with a square planar shape? (1 mark)
90 degrees
How many lone/bonded pairs of electrons does a molecule with a square planar shape have? (2 marks)
4 bonded
2 lone
Which elements form a square planar shape? (3 marks)
Au
Pt
Pd
