Electronegativity

Question 1

Electronegativity

Answer 1

The measure of the ability of a bonded atom to attract the pair of electrons in a covalent bond

Question 2

Trends in electronegativity across a period

Answer 2

Increases across a period

Question 3

Reason for periodic trend

Answer 3

• Nuclear charge increases (no. of protons increases)
• Atomic radius decreases (because of attraction between nucleus and outer electron increases)
• Electron shielding remains the same (no. of inner shells stay the same. Electrons are negatively charged and so inner-shell electrons repel outer-shell electrons)
• Nuclear attraction experienced by the bonding electrons increases (attraction between nucleus and outer electron )

Question 4

Trends in electronegativity in a group

Answer 4

Decreases down a group.

Question 5

Reason for groupq trend

Answer 5

• Despite nuclear charge increasing, atomic radius increases/increases in electron shells.
• Electron shielding increases
• As a result electrostatic attraction between the nucleus and the bonding electrons decreases, which in turn decreases the ability of an atom to attract electrons towards itself

Question 6

Permanent dipole

Answer 6

There is a small charge difference across a bond resulting from a difference in electronegativities of the bonded atoms.

Question 7

δ+

Answer 7

Positive Dipole
This means there is slightly positive charge on the an atom (the least electronegative atom always has a δ+)

Question 8

δ-

Answer 8

• Negative dipole.
• This means there is slightly negative charge on an atom (the more electronegative atom always has a δ- because it’s able to attract more electrons towards itself)

Question 9

Non polar bonds

Answer 9

• Bonded electron pair is shared equally between bonded atoms.
• If the polar bonds are arranged symmetrically the partial charges cancel out and the molecule is non-polar.
• A bond will be non-polar when the bonded atoms are the same and the bonded atoms have the same or similar electronegativity

Question 10

Polar Bonds

Answer 10

• are arranged asymmetrically, the partial charges do not cancel out and the molecule is polar.
• The bonded electron pair is shared unequally between the bonded atoms.
• A bond will be polar when the bonded atoms are different and have different electronegativity values