Section 3 - Polarity

Question 1

The ability of an atom to attract electrons in a covalent bond is called its ______________.

Answer 1

electronegativity

Question 2

Ignoring Group 0, how does electronegativity decrease/increase through groups and periods?

Answer 2

Electronegativity decreases down a group in the periodic table, and increases across a period.

Question 3

What is the most electronegative element?

Answer 3

Fluorine

Question 4

In a bond between two different elements with different electronegativities, what atom will the bonding electrons be more strongly attracted towards?

Answer 4

The atom with the higher electronegativity.

Question 5

What is a polar bond?

Answer 5

A bond between two different elements with different electronegativities, where the bonding electrons are attracted more strongly towards the atom with the higher electronegativity.

Question 6

Why does the boiling point of methane increase if you substitute a chlorine atom for one of the hydrogen atoms?

Answer 6

The chlorine atom polarises the molecule, making one end slightly positive and the other slightly negative. The oppositely charged ends of different molecules attract each other, so more energy is required to separate them. This results in an increase in boiling point.

Question 7

What is the strongest type of of intermolecular force?

Answer 7

Hydrogen bonding

Question 8

Molecules that contain a ________, _________, or _________ atom bonded to a hydrogen atom can form strong intermolecular bonds.

Answer 8

Fluorine, oxygen, nitrogen

Question 9

Why are hydrogen bonds the strongest type of intermolecular force?

Answer 9

This is because the hydrogen atoms are strongly polarised by the very electronegative fluorine, oxygen or nitrogen atoms. These slightly positive hydrogen atoms are attracted to the lone pair of electrons on a F, O or N atom in a nearby molecule to form an attraction known as a hydrogen bond.