Lecture 2

Question 0

What electrons have the largest principle quantum number?

Answer 0

The valence electrons

Question 1

What is a molecule?

Answer 1

Individual atoms joined together

Question 2

What occurs in a covalent bond?

Answer 2

• just right interactions
• minimised e-e repulsions
• optimise attraction
  Stable molecule

Question 3

What will happen if the covalent bond is pushed further?

Answer 3

Becomes an unstable molecule

Question 4

What is usually considered the ‘best’ Lewis structure?

Answer 4

The one that obeys the octet rule

Question 5

What is the octet rule?

Answer 5

Atoms try to complete their octets by sharing electrons, so the atoms are surrounded by 8 electrons

Question 6

What elements can have more than an octet?

Answer 6

Heavier elements like Si, P, S

Question 7

What is a formal charge?

Answer 7

Valence electrons in the free atom (started with) minus electrons which have been assigned to the Lewis structure.

Question 8

Is there more than one way to minimise a formal charge?

Answer 8

Yes

Question 9

What does it mean if a molecule has resonance structures?

Answer 9

More than one equivalent Lewis structures can be drawn.
Actual binding is an average of all possibilities.
Eg double bonds in different places