Electronegativity

Question 1

what is a covalent bond?

Answer 1

a covalent bond is shared pair of electrons

Question 2

why aren’t electrons shared equally?

Answer 2

because some atoms have a stronger pull on them than others

Question 3

define electronegativity

Answer 3

electronegativity is the power of the atom to attract the bonding electrons in a covalent bond to itself

Question 4

why does electronegativity increase across a period?

Answer 4

each atom has one more proton in its nucleus (there are also extra electrons, but these go into the same shell due to being in the same period) so they don’t shield each other from this extra positive charge in the nucleus, so the nucleus attracts the bonding electrons more strongly.

Question 5

why don’t noble gases have an electronegativity value?

Answer 5

since they cannot form a covalent bond due to their full outer shell.

Question 6

why does electronegativity decrease going down a group?

Answer 6

going down a group each atom has one more electron shell, so the bonding electrons are further from the nucleus and more shielded from its positive charge, hence attracted les by the nucleus (despite more protons)

Question 7

what are the 4 most electronegative elements?

Answer 7

F (4.0)
O (3.5)
N, Cl (3.0)

Question 8

what are the two extremes on the bonding spectrum?

Answer 8

(purely) ionic bonding => (purely) covalent bonding

Question 9

what is purely ionic bonding?

Answer 9

• complete electron transfer
• big difference in electronegativity between the molecules
• E.g metals + non metal

Question 10

what is purely covalent bonding?

Answer 10

• electrons are shared evenly
• atoms are equal in electronegativity
• E.g. Cl2, O2, Br2, N2

Question 11

what is a polar covalent bond?

Answer 11

covalent bonds, with ionic character, where the electron pair is not evenly shared, as the two bonding atoms are not equal in electronegativity (but not hugely different as then it would be ionic)

Question 12

how polar is a bond?

Answer 12

a covalent bond will be polar if the two bonded atoms are different in electronegativity, the bigger the difference the more polar the bond.

Question 13

will a molecule have an overall dipole? (be polar overall)

Answer 13

some molecules contain polar bonds but are non-polar overall, this happens if the bonds are arranged symmetrically so the dipoles cancel.
E.g
O=C=O, CO2