6.2 electronegativity and polarity

Question 1

what is electronegativity measured in

Answer 1

Electronegativity is often measured on the Pauling scale (of electronegativity). The
image below shows the values of electronegativity for individual atoms. The higher the
number the better the atom is at attracting the shared pair of electrons.

Question 2

what impacts electronegativty

Answer 2

* nuclear charge:The greater the number of protons in a nucleus, the greater the attraction to the electrons in the covalent
bond, resulting in higher electronegativity.
However, full energy levels of electrons shield the
electrons in the bond from the increased attraction of the greater nuclear charge, thus reducing electronegativity.
* atomic radius: As radius of an atom increases, the bonding pair of electrons become further from the nucleus. They are
therefore less attracted to the positive charge of the
nucleus, resulting in a lower electronegativity.

Question 3

define

electronegativity

Answer 3

The ability of the atom in a covalent bond to attract the shared pair electrons towards itself is called the electronegativity

Question 4

electronegativity along the periodic table

whats the pattern

Answer 4

• Electronegativity decreases down a group
• Electronegativity increases across a period

Question 5

Electronegativity decreases down a group
because…

Answer 5

• Atomic radius increases.
• Distance between outer shell and
  nucleus increases.
• More effective shielding between
  nucleus and outermost shell.
• Weaker attraction on the shared pair of
  electrons

Question 6

Electronegativity increases across a period
because…

Answer 6

• Atomic radius reduces (slightly) due to a
  greater nuclear charge (more protons).
• Distance between outer shell and nucleus
  decreases.
• Constant shielding between nucleus and
  outermost shell.
• Greater attraction on the shared pair of
  electrons

Answer 7

A bond between atoms of similar electronegativity (a small difference) is likely to
be COVALENT

A bond between atoms of very different electronegativity (a large difference) is
likely to be IONIC.

Covalent 0
polar covlent dif of 0 - 1.8
ionic dif greater than .8

Question 8

define

polar

Answer 8

When the bonded electron pair is shared unequally between the bonded atoms. A
bond will be POLAR.

Question 9

NON-POLAR

Answer 9

When electrons are shared equally there is no difference in the electron density on
one atom vs the other – the electronegativity is zero, or very close to zero.

Question 10

dipole.

Answer 10

The separation of opposite charges in the molecule is
known as a

Question 11

rules of polarity

Answer 11

Carbon and hydrogen have similar electronegativities and DO NOT form polar bonds.

Most commonly, carbon or hydrogen bonded to fluorine, oxygen, nitrogen, chlorine or
bromine form POLAR BONDS.

If a molecule contains polar bonds but the shape of the molecule is symmetrical the
dipoles cancel and the molecule is non-polar.