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Slide 1

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Intermolecular forces hold molecules
together. Some of these
intermolecular forces are down to
polarisation.…read more

Slide 2

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What is electronegativity?
· A covalent bond is a shared pair of electrons but are these
electrons shared equally between the two bonded atoms?
· The answer is yes if the two atoms are of the same element.
In molecules such as H2 and CL2 the bonding electrons are
shared equally.
· But not if the two bonded atoms are different elements.
One of the bonded atoms has more of a share of the
bonding electrons than the other. This happens if the two
atoms have a different electronegativity.
Electronegativity is the ability to attract the
bonding electrons in a covalent bond…read more

Slide 3

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Fluorine is the most electronegative element. Its
electronegative value is 4.0 on the Pauling scale. In
general electronegativity increases from left to right
across the period and as you go up each group.
Electronegativity cannot
be measured directly
instead it has to be
calculated. The most
common way is the
Pauling electronegativity
scale named after a
scientist who devised it.…read more

Slide 4

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In a polar bond, the difference In a covalent bond
in electronegativity between between two atoms
two atoms causes a dipole. A of different
dipole is a difference in electronegativity's
charge between the two the bonding
atoms caused by a shift in electrons are pulled
electron density in the bond. towards the more
atoms. This makes
the bond polar.
The symbol shows
the weak
electrostatic forces
of attraction
between molecules.…read more

Slide 5

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In other words when the bonding pair of
electrons is not shared equally, the bond is a
polar bond. The more electronegative atom
gains a partial negative charge (-). The less
electronegative atom gains a partial positive
charge (+).
e g . polar bond in hydrogen chloride
Chlorine is more
electronegative than
hydrogen. The
molecule has a
dipole, a pair of
separated charges of
opposite signs.…read more

Slide 6

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There are many types of
intermolecular forces
Hydrogen bonding
Permanent dipole-dipole
Induced dipole-dipole
Van der Waals…read more

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