L.1 2. VSEPR

Question 1

What is the Octet Rule?

& Exceptions?

Answer 1

• Atoms form bonds with other atoms to complete 8 electrons in their outer shell
• Incomplete octet
  
  • Hydrogen 2
  • Helium 2
  • Lithium 2
  • Beryllium 4
  • Boron 6
• Expanded
  
  • Period 3 & Beyond + 8 Electrons
  • P 10
  • S 12
  • Cl 14
• Odd Number of electrons
  
  • NO

Question 2

What is Ionic bonding?

What does it form?

Answer 2

• Metal + Non-metal
• Low Ionization Energy Atom + High Electron Affinity Atom
• Cation + Anion
• Electrostatic Attraction between ions causes them to remain in close proximity
• Crystalline Lattices

Question 3

What is Covalent Bonding?

Name the 3 types of covalent bonding.

Answer 3

Electron Pair Sharing between two atoms of similar electronegativities

• Non-polar Covalent; Equal Sharing of electrons
• Polar Covalent; Unequal sharing of electrons
• Coordinate Covalent; Both electrons being shared are provided by ONE of the Atoms

Question 4

What is Bond Order?

Rank; Bond Length & Bond Strenght.

Answer 4

Refers to whether a covalent bond is a

single bond, double bond, or a triple bond.

Single bond = Long = Weakest

Double = Medium = Medium

Triple = Shortest = Strongest

Question 5

What is Polarity?

Answer 5

Two atoms having a large difference in their

electronegativity within a molecule.

• All polar molecules contain polar bonds
• Non-polar molecules may contain polar bonds or non-polar bonds with dipole moments that cancel each other.

Question 6

What is Non-Polar Covalent Bonding

+

Describe the scale (difference in polarity) of the 3 different types of bonds.

Answer 6

No separation of charges across a bond

H₂ N₂ O₂ F₂ Cl₂ Br₂ I₂

_{Non-Polar. 0 - 0.5}

_{Polar 0.5 - 1.7}

_{Ionic 1.7 +}

Question 7

Formal Charges

Answer 7

Exist when an atom is surrounded

by more or fewer valence electrons that it has in its neutral state

(assuming equal sharing of electrons in a bond)

Question 8

Resonance Structures

Answer 8

For any molecule with a pi system of electrons,

resonance structures exist;

these represent all of the possible configurations of electrons

• stable and unstable
• that contribute to the overall structure

Question 9

VSEPR

Answer 9

Valence shell electron pair repulsion

predicts the three-dimensional molecular geometry of covalently bonded molecules.

Electrons whether bonding or non-bonding arrange themselves as fas as possible from each other.

For MCAT know

H C N O F S P Si Cl

Question 10

Electronic Geometry

vs

Molecular Geometry

Answer 10

Electronic Geometry; Bonding and Non-bonding electron position

Molecular Geometry; Only bonding electron positions

Question 11

Describe the Sigma & Pi Bonds

Answer 11

Sigma = Head-to-head overlap of orbitals

Pi = overlap of two parallel electron cloud densities

Question 12

Strongest to Weakest Intermolecular forcer

Answer 12

Hydrogen (Strongest)

Involved in intra- and intermolecular attraction; hydrogen bonding occurs with Fluorine, Oxygen or Nitrogen.

Dipole-Dipole (Medium)

Oppositely charged ends of polar molecules, evident in solid and liquid phases but negligible in the gas phase due to the distance between particles

London dispersion forces (Weakest)

Present in all atoms and molecules. As the size of the atom or structure increases, so does the corresponding London force.

Question 13

Dipole Moment Equation

Answer 13

P = qd

Dipole moment =

The magnitude of charge x Displacement Vector separating the two charges

Question 14

5 Electronic Geometries as predicted by VSEPR and Angles

Answer 14