Polarity

Question 1

Electronegativity

Answer 1

The ability of an atom to attract the bonding electrons in a covalent bond

Question 2

What measures electronegativity?

Answer 2

The Pauling scale

Question 3

What element has the highest electronegativity?

Answer 3

Fluorine

Question 4

What causes an atom of an element to have high electronegativity?

Answer 4

If it has higher nuclear charge but small atomic radius

Question 5

Trend in electronegativity across the periodic table

Answer 5

Decreases down the group
increases across the period

Question 6

What can happen to covalent bonds if there is a different in electronegativity across the atoms?

Answer 6

The bond can be polarised

Question 7

What causes a polar bond?

Answer 7

When atoms of 2 different electronegativities bond, the bonding electrons are pulled to more electronegative atom
Thus electrons spread unevenly in the bond = an opposite charge at different ends

Question 8

How are differences in charge across a polar bond shown?

Answer 8

More electronegative element is slightly negative (d-) because bonded electrons are attracted more strongly to it
Less electronegative element is slightly positive (d+) because bonded electrons drawn away from it
=opposite charges at ends of molecule

Question 9

How is a polar covalent bond shown?

Answer 9

An arrow from the positive charged atom to negative charged atom to represent electrons moving away to mor electronegative element

Question 10

What is the difference in charge across the 2 atoms called?

Answer 10

A dipole

Question 11

Dipole

Answer 11

A difference in charge between 2 atoms caused by a shift in electron density in the bond, separated by a small distance

Question 12

What causes a greater polar bond?

Answer 12

A larger difference in electronegativity across the molecule because there is a greater shift in electron density

Question 13

What covalent bonds are non polar?

Answer 13

When atoms of the same element bond so no difference in electronegativity
Or if the atoms of the elements electronegativity is so small it is essentially non polar

Question 14

Where do electrons sit in the covalent bond if the bond isn’t polar?

Answer 14

Midway because they area attracted the same amount to both atoms

Question 15

What are the extremes on the continuum of bond types?

Answer 15

Purely ionic character
Purely covalent

Question 16

Where do polar bonds lie in the continuum of bond type?

Answer 16

In the middle, neither purely covalent or ionic dependent on the difference in electronegativity

Question 17

In a polar bond, what causes a higher % of ionic character?

Answer 17

If the difference in electronegativity (on the Pauling scale) between 2 atoms of different elements is much higher
Because this shows a greater shift in electron density thus more polar bond

Question 18

In a polar bond, what causes a lower % of ionic character?

Answer 18

If the difference in electronegativity (on the Pauling scale) between 2 atoms of different elements is low
Because this shows a lesser shift in electron density thus less polar bond

Question 19

What bonds can be purely covalent?

Answer 19

Atoms of single elements eg diatomic gases eg Cl2
Because the electronegativity difference is 0 thus bond isn’t polar and there is no shift in electron density = no dipole

Question 20

How to find the % ionic character of a bond?

Answer 20

Find the electronegativities of each element in the bond
Find the difference between these
Correlate this number in the table given to find % ionic character

Question 21

If a molecule has polar bonds does that make the molecule a polar molecule?

Answer 21

Not necessarily

Question 22

What determines if a molecule is considered polar?

Answer 22

If the molecule contains polar bonds and has a certain shape where the dipoles are not cancelled out

Question 23

How shape effects the overall polarity of a molecule

Answer 23

The molecule must have an overall dipole acting in the same direction so the dipoles reinforce each other

Question 24

How can a molecule have polar bonds but not be overall a polar molecule?

Answer 24

If the polar bonds act in opposite directions to each other = cancels out so no overall dipole