Electronegativity and Polarity

Question 1

What is electronegativity and how is it measured

Answer 1

The ability of an atom in a covalent bond to attract the bonding pair of electrons. It is measured using Pauling’s electronegativity values

Question 2

How does electronegativity change across periodic table

Answer 2

Increases across period up to group 7 and decreases down group

Question 3

Which is the most electronegative element

Answer 3

Fluorine

Question 4

Three factors affecting electronegativity

Answer 4

-nuclear charge
-atomic radius
-shielding

Question 5

How does nuclear charge affect electronegativity

Answer 5

-more protons means stronger electrostatic force of attraction between nucleus and bonding pair of electrons, greater electronegativity

Question 6

How does atomic radius affect electronegativity

Answer 6

Smaller the atomic radius the closer the nucleus to the bonding pair meaning stronger force of electrostatic attraction between the two, greater EN

Question 7

How does shielding affect electronegativity

Answer 7

Less shells of electrons between the nucleus and bonding pair of electrons means less shielding so less repulsion meaning stronger force of attraction

Question 8

Why does electronegativity decrease down group

Answer 8

As atomic radius increases and more shielding so less attraction between nucleus and bonding pair which outweighs the increase in nuclear charge

Question 9

Why does electronegativity increase across period

Answer 9

Atomic radius decreases and nuclear charge increases so stronger force of attraction between nucleus and bonding pair, electrons added to same shell so shielding does not increase significantly

Question 10

How does atomic radius change down group and across period

Answer 10

-increases down group
-decreases across period

Question 11

What is a non-polar bond

Answer 11

Bond formed when electrons are shared equally between two atoms(dif in electronegativity between the two atoms must be very small or zero)

Question 12

What is a polar bond

Answer 12

Bond formed when a bonding pair of electrons are not shared equally, due to difs in electronegativity the shared electrons are pulled towards atom with higher electronegativity by greater amount

Question 13

Why do polar bonds have a positive and negative pole

Answer 13

-delta negative side has slight excess of negative charge and delta positive side is where electrons are less strongly attracted

Question 14

What is a purely covalent bond

Answer 14

When the electron pair is shared equally between two atoms with the same electronegativities

Question 15

What is purely ionic bonding

Answer 15

Giant lattice of spherical ions held together by electrostatic forces of attraction, with the electron transfer from reactive metal to highly electronegative non-metal so large difference in electronegativity

Question 16

What is polarisation in ionic bonding

Answer 16

When small and highly charged (high charge density) cations distort electron clouds of anions causing partial covalency as electrons are attracted to this cation

Question 17

What is a polar covalent bond

Answer 17

Bond in which the atoms have slightly different electronegativities so an unequal attraction for electrons so sharing is unequal

Question 18

Order of type of bonding from atoms with very different electronegativities so the same electronegativity

Answer 18

-purely ionic (very different electronegativity)
-ionic bonding with polarisation
-polar covalent bonding
-purely covalent (identical electronegativity)

Question 19

What is Pauling’s electronegativity scale and what is the value for fluorine

Answer 19

-from 0 to 4 for electronegativity with fluorine being the most electronegative with a value of 4.0

Question 20

When does a bond become ionic

Answer 20

When the difference in electronegativity between the two atoms is large enough for the more electronegative element to remove electrons completely from the less electronegative atom

Question 21

What is a polar molecule

Answer 21

Molecule that contains polar bonds which do not cancel each other out so the whole molecule is polar and has a positive and negative electric pole called a dipole

Question 22

Which molecules have an overall dipole moment

Answer 22

Polar molecules in which their polar bonds do not cancel each other out so there is an overall twisting effect