Bonding L8

Question 1

Exceptions to the Octet rule

Answer 1

• B=6
• P=10
• S=12
• XE=12 with 2 lone pairs

Question 2

Expanded octets

Answer 2

• Atoms in periods 3 through 7 can bond with other atoms in such a way that they end up with more than eight electrons in their octets
• they are able to do this because they have d-orbitals in their outer shells that can accept electrons
• Have d/p sub levels that electrons spill over
• electrons can flow into D bc p+d orbitals are similar in energies

Question 3

Formal charge

Answer 3

• In some cases, the atoms in a molecule can be assembled in different ways when drawing a lewis diagram
• Formal charges are calculated to identify the most stable or likely structure
• The sum of the formal charges on each atom will be zero for a neutral molecule
• The sum of the formal charges on each atom will be equal to the overall charge of the structure for a polyatomic ion

Question 4

How to tell which structure is more likely from formal charge

Answer 4

1. The more likely Lewis structure will have formal charges that are closer to or equal to zero
2. If there are negative formal charges, they should reside on the more EN elements in the structure

Question 5

Calculating formal charge

Answer 5

the number of valence electrons assigned to the neutral atom- the number of electrons assigned to the atom in the structure

Question 6

Bond Energy potential energy

Answer 6

• The potential energy of valence electrons decreases as they approach the nucleus of an atom
• e- bond because they have lower energy so the closer they get the less energy they have

Question 7

Bond energy

Answer 7

• Energy is released during the formation of a bond
• Potential energy decreases as the atoms move closer together
• The same amount of energy must be added in order to break that specific bond
• Potential energy increases as the atoms move away from one another
• The amount of energy that is required to break the bond between two specific atoms in a molecule
• equal to the amount of energy released when a bond forms between the same two atoms
• Exothermic= negative bond formed
• Endothermic- positive bonds break

Question 8

Bond energy/bond length

Answer 8

• As the atomic radii of bonding atoms increase, the bond length increases and the bond energy decreases
• A closer proximity to the shared electrons allows for a stronger force of attraction between protons and bonding electrons
• when the force of attraction is greater, it requires more energy to break the bond

Question 9

Bond energy/Bond Length

Answer 9

• as the number of bonds between two atoms increases, the bond length decreases and the bond energy increases
• As the number of bonds between two atoms increases, the bond energy increases, the bond length decreases, and the PE decreases

Question 10

Bond order

Answer 10

• Bond order is the number of bonds between two atoms (single, double, triple)
• When bond order increases:
• The bond length decrease
• The PE associated with the bond decreases
• The bond energy increases

Question 11

Molecular Models

Answer 11

• Space filling model

- Ball and stick model

Question 12

Resonance structures

Answer 12

• for many molecules, double or triple bonds can be located between different atoms
• This results in two or more possible Lewis Diagrams that are equally valid

Question 13

How to find bond order

Answer 13

bonds/#atoms around central

Question 14

Limitations to the lewis structure

Answer 14

in some cases, resonance must be used to refine a lewis structure in order to obtain qualitatively accurate predictions about the effective number of bonds, bond energy, and bond length