Shapes of molecules and intermolecular forces
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Explain the electron pair repulsion theory
Electrons surrounding an atom determine the shape of the atom Electron pairs repel one another so that they are arranges as far apart as possible Arrangement of electrons minimises repulsion and creates a definite shape
What does a solid line represent?
Represents a bond on the plane of the paper
What does a solid wedge represent?
Represents a bond coming out the plane of the paper
What does a dotted wedge represent?
Represents a bond going into the plane of the paper
Where are lone pairs located in relation to central atom?
Closer to the central atom as occupies more space
What electrons repel more strongly?
Lone pairs
Explain a tetrahedral shape
4 bonded pairs No lone pairs Bond angle 109.5
Explain a pyramidal shape
3 bonded pairs One lone pair Bond angle 107
Explain a non-linear shape
2 bonded pairs 2 lone pairs Bond angle 104.5
Explain a linear shape
2 bonded regions No lone pairs Bond angle 180
Explain a trigonal planar shape
3 bonded regions No lone pairs Bond angle 120
Explain an octahedral shape
6 bonded regions No lone pairs Bond angle 90
What shape are carbonate and nitrate ions?
Trigonal planar
What shape are sulphate ions?
Tetrahedral
Define ‘electronegativity’
A measure of attraction of a bonded atom for the pair of electrons in a covalent bond
What are the most electronegative elements?
Fluorine Oxygen Nitrogen Chlorine
What scale is electronegativity measured on?
Pauling electronegativity scale
How does electronegativity affect whether the bond is ionic or covalent?
The greater the difference electronegativity value is the more likely it is to be ionic because one bonded atom will have a much greater attraction for shared pair of electrons
What does it mean for a bond to be non-polar?
The bonded electron pair is shared equally between the bonded atoms
When do non-polar bonds occur?
The bonded atoms are the same The bonded atoms are the same or have a similar electronegativity value
What is a pure covalent bond?
The bonded atoms come from the same element and the bond is shared equally
What is a polar bond?
The bonded electron air is shared unequally between the atoms
What is polar covalent bond?
Bonded atoms are different and there is a difference in electronegativity values
Define ‘dipole’
Separation of opposite charge