Bond polarity

Question 1

What is electronegativity?

Answer 1

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

Question 2

How does electronegativity change across a period?

Answer 2

Electronegativity increases along a period:
* Proton number increases but shielding stays constant
* Atomic radius decreases
* Attraction to shared pair of electrons increases

Question 3

How does electronegativity change down a group?

Answer 3

Electronegativity decreases down a group:
* Increased number of shells which increases shielding
* Atomic radius also increases
* This outweighs the increase in proton number
* Attraction to shared pair of electrons decreases

Question 4

Order of electronegativity

Answer 4

Order of electronegativity:
F > O > N > Cl > Br > C similar to H

Question 5

What is the relationship between ionic and covalent bonds?

Answer 5

Ionic and covalent bonding are the extremes of a continuous scale of bonding

• Very high electronegativity difference = ionic bonding
• Medium electronegativity difference = polar covalent bonding
• Similar electronegativity = covalent bonding

Question 6

How to identify polar molecules

For two atoms and more than two atoms

Answer 6

For two atoms:

• If the atoms have different electronegativity the molecule as a whole is polar

More than two atoms:

• If the shape is symmetrical (shape needs to be stated) dipols created by the polar bonds are cancelled out, molecule will have symmetrical electron cloud and be non-polar.
• If the shape is asymmetrical, the dipols created by the polar bonds are not cancelled out, the molecule will have an asymmetrical electron cloud and will be polar