2.6.2: electronegativity and polarity

Question 1

what’s electronegativity?

Answer 1

the attraction of a bonded atom for the pair of electrons in a covalent bond

Question 2

what’s the trend of electronegativity on the periodic table?

Answer 2

electronegativity increases up and across the periodic table

Question 3

what’s electronegativity like in molecules of the same element e.g. O2

Answer 3

the bonded electron pair is shared equally because the atoms are the same element

Question 4

what atoms form non-polar bonds?

Answer 4

atoms of the same element (pure covalent bonds)

atoms with very similar electronegativities e.g. hydrocarbon liquids like hexane, C6H14

Question 5

what’s electronegativity like in molecules where the atoms are different elements?

Answer 5

the bonded electron pair is shared unequally because the nuclear charges are different and the atoms may be different sizes so the shared pair of electrons may be closer to one nucleus because it experiences more attraction from one of the bonded atoms

Question 6

what atoms form polar bonds?

Answer 6

molecules where the atoms are different elements because they will have a large difference in electronegativity

Question 7

example of a polar bond

Answer 7

hydrogen chloride
hydrogen has an electronegativity of 2.1 and chlorine has an electronegativity of 3.0 - chlorine is more electronegative so has a greater attraction for the bonded pair of electrons

Question 8

what does it mean that HCl is polarised?

Answer 8

it has a permanent dipole

Question 9

why do some molecules containing polar bonds have no overall polarity?

Answer 9

because they’re symmetrical and the dipoles cancel out

Question 10

what are the most electronegative atoms?

Answer 10

non-metals

fluorine is the most electronegative

Question 11

what are the least electronegative atoms?

Answer 11

group 1 metals