Bonding

Question 1

What is electronegativity?

Answer 1

The power of an atom to attract the 2 electrons in a covalent bond

Question 2

3 factors affecting electronegativity?

Answer 2

• nuclear charge
• atomic radius
• shielding

Question 3

How is the power of an atoms’s electronegativity reflected by?

Answer 3

A value on the Pauling scale from 0.7 to 4.0. The higher the value, the greater the power.

Question 4

What’s a use of electronegativity?

Answer 4

It helps us understand better, the bonding in a substance

Question 5

How do you work out the shape of a molecule?

Answer 5

1. ((group num of central atom) + (num of other atoms))/2 = total num of pairs of electrons
2. num of atoms around central atom = num of bonding pairs
3. total num of pairs - num of bonding pairs = num of lone pairs
   (If the molecule was a cation you would minus the charge when doing step 1, if the molecule was an anion you would add the value of charge in step 1)

Question 6

What repels more and why, lone pairs or bonding pairs?

Answer 6

Lone pairs repel more than bonding pairs because they are close to the central atom and the negative charge is more concentrated.

Question 7

Explain how van der Waals forces occur.

Answer 7

• random electron movement induces a temporary dipole
• The dipole induces slight positive and negative charges in the adjacent molecules
• This causes weak electrostatic charges between them

Question 8

What affects the strength of van der Waals forces?

Answer 8

The Mr of a substance
- The higher the MR, the more electrons it has
- the more electrons, the more temporary dipoles are induced
- the more dipoles the stronger the forces are
(when Mr is the same) Contact surface area
- The more contact surface area, the stronger the forces are
- The less branched a molecule is, the larger the contact surface area
(unbranched molecules tend to have higher boiling points if Mr is same)

Question 9

What do you need for there to be a permanent dipole-dipole attraction?

Answer 9

The two molecules need to be polar

Question 10

As the difference in electronegativity increases, what type of bonding becomes more probable?

Answer 10

The probability of ionic bonding occurring increases as the difference in electronegativity increases

Question 11

Describe Hydrogen bonding.

Answer 11

• A type of permanent dipole-dipole interaction
• Occur between H atom and a very electronegative atom (F, O, N)
• There is a strong attraction between the lone pair of one atom and the H atom
• H bonding is an intermolecular force, not a bond

Question 12

Ranks the types of intermolecular bonding from strongest to weakest.

Answer 12

H-bonding > permanent dipole-dipole > van der waals