Electronegativity

Question 1

What scale is electronegativity measured on?

Answer 1

Electronegativity is usually measured using the Pauling scale.

Question 2

What is the most electronegative element?

Answer 2

Fluorine is the most electronegative element.

Question 3

What is a dipole?

Answer 3

A dipole is a difference in charge between the two atoms caused by a shift in electron density in the bond.

Question 4

Why isn’t CO2 a polar molecule, even though it has polar bonds?

Answer 4

The polar bonds are arranged so they point in opposite directions, and therefore cancel each other out.

Question 5

Define the term electronegativity.

[1 mark]

Answer 5

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

Question 6

What are the trends in the electronegativity as you go across a period and down a group in the periodic table?
[1 mark]

Answer 6

Electronegativity increases across a period and decreases down a group.

Question 7

Explain whether or not the molecules in boron trichloride (BCl3) and dichloromethane (CH2Cl2) have an overall dipole.
[2 marks]

Answer 7

• The polar bonds in BCl3 are arranged so that they cancel each other out, so the molecule has no overall dipole.
• CH2Cl2 does have an overall dipole because the polar bonds are not orientated so they are pointing in opposite directions so they don’t cancel each other out.