intermolecular forces

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A-Level Chemistry Flashcards on intermolecular forces, created by owen.strafford on 30/11/2015.
owen.strafford
Flashcards by owen.strafford, updated more than 1 year ago
owen.strafford
Created by owen.strafford over 8 years ago
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Question Answer
Describe the shape of a trigonal planar molecule ? -It has 3 electron pairs, -120 degrees bonding angle, - 0 lone pairs.
Describe the shape of a tetrahedral molecule ? - It has 4 electron pairs, - 109.5 degree bonding angle, - 0 lone pairs.
Describe the shape of a Octahedral molecule ? - It has 6 electron pairs, - 90 degree bond angle, - 0 lone pairs.
Describe the shape of a Pyramidal molecule ? - It has 3 electron pairs, - 107 degree bonding angle, - 1 lone pair.
Describe the shape of a Non-linear molecule ? - It has 2 electron pairs, - 104.5 bonding angle, - 2 lone pairs.
What does a lone pair do to the shape of a molecule ? the lone pairs repel more than a bonding pair therefore it decreases the bonding angle by repulsing the bonding pairs closer together.
What is the definition for electronegativity ? the tendency of an atom to attract electrons in a covalent bond.
Describe what happens when 2 bonding atoms are different ? If the bonding atoms are different, one of the atoms is likely to attract the bonding electrons more. The bonding atom with a greater attraction for the electron pair is more electronegative.
Is BF3 polar or non-polar? It is non-polar because the shape is symmetrical and so the dipoles cancel out.
Is PF3 polar or non-polar? It is polar because the shape is non-symmetrical and so the dipoles don't cancel out.
What are intermolecular forces ? Forces that are weaker than ionic and covalent bonds, they are caused by weak attractive forces between very small dipoles in different molecules.
What are the 3 common types of intermolecular forces ? - Hydrogen bonds, - Permanent dipole-dipole , - London forces.
What is a Permanent dipole-dipole interaction? Its a weak attractive force between permanent dipoles in neighbouring polar molecules.
What is an induced dipole-dipole force? Are weak intermolecular attractions between very small, temporary dipoles in neighbouring molecules.
What are London Forces ? They are attractive forces between induced dipoles in neighbouring molecules.
Describe the why London forces create a chain reaction ? the movement of electrons causes a instantaneous dipole to be formed across a molecule. This instantaneous dipole will induce a dipole in the neighbouring molecule, this then forms a chain of temporary dipoles.
How do you increase London forces? The greater number of electrons the larger the induced dipole, therefore the greater the attractive forces between molecules. (Therefore the boiling points increase.)
What are the 2 bonds that make a hydrogen bonds ? 0-H and N-H
What are the hydrogen bonds like in a molecule? They're permanent dipoles and are polar.
How does the Hydrogen bonds work? The electron deficient delta H+ on one molecule attracts the lone pair of electrons on the delta O- or the delta N- on a different molecule.
What is the ice-lattice structure ? its an open network of H20 molecules, Oxygen has 4 bonds: - 2 covalent bonds, - 2 hydrogen bonds, - makes 6 sided shape.
Why does a lone pair of electrons repulse more than a bonding pair of electrons ? Because the lone pair of electrons is slightly more electron dense than the bonding pairs of electrons.
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