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# Chapter 10

### Chemical Bonding II: Molecular Shapes and Valence Bonding Theory (Test 4)

Question | Answer |
---|---|

What is the simplest scientific model for understanding bonding in molecules? | Lewis Structures and the Octet Rule |

What does VSEPR stand for? | valence shell electron pair repulsion |

What is the main idea behind VSEPR? | Electron pairs are mutually repulsive, and therefore they will automatically adopt a shape allowing them to get as far apart as possible. |

How many electron groups does a bond (single, double, triple) count as? | 1 |

How many electron groups does a pair of electrons count as? | 1 |

What is the electron pair geometry for two electron groups? What is the angle? What is the hybridization? | linear; 180 degrees; sp |

What is the electron pair geometry for three electron groups? What is the angle? What is the hybridization? | trigonal planar; 120 degrees; sp^2 |

What is the electron pair geometry for four electron groups? What is the angle? What is the hybridization? | tetrahedral; 109.5 degrees; sp^3 |

What is the electron pair geometry for five electron groups? What is the angle? What is the hybridization? | trigonal bipyramidal; 90 and 120 degrees; sp^3d |

What is the electron pair geometry for six electron groups? What is the angle? What is the hybridization? | octahedral; 90 degrees; sp^3d^2 |

What is the molecular geometry and angle of a molecule with two bonding pairs of electrons? | linear; 180 degrees |

What is the molecular geometry and angle of a molecule with three bonding pairs of electrons? | trigonal planar; 120 degrees |

What is the molecular geometry and angle of a molecule with two bonding pairs and one lone pair of electrons? | bent; less than 120 degrees |

What is the molecular geometry and angle of a molecule with four bonding pairs of electrons? | tetrahedral; 109.5 degrees |

What is the molecular geometry and angle of a molecule with three bonding pairs and one lone pair of electrons? | trigonal pyramidal; less than 109.5 degrees |

What is the molecular geometry and angle of a molecule with two bonding pairs and two lone pair of electrons? | bent; less than 109.5 degrees |

What is the molecular geometry and angle of a molecule with five bonding pairs of electrons? | trigonal bipyramidal; 90 and 120 degrees |

What is the molecular geometry and angle of a molecule with four bonding pairs and one lone pair of electrons? | see-saw; less than 90 and less than 120 degrees |

What is the molecular geometry and angle of a molecule with three bonding pairs and two lone pair of electrons? | T-shaped; less than 90 degrees |

What is the molecular geometry and angle of a molecule with two bonding pairs and three lone pair of electrons? | linear; 180 degrees |

What is the molecular geometry and angle of a molecule with six bonding pairs of electrons? | octahedral; 90 degrees |

What is the molecular geometry and angle of a molecule with five bonding pairs and one lone pair of electrons? | square pyramidal; less than 90 degrees |

What is the molecular geometry and angle of a molecule with four bonding pairs and two lone pair of electrons? | square planar; less than 90 degrees |

How do the repulsions of lone pairs compare to those of bonded pairs? | Lone pairs are more repulsive than bonded pairs. |

How do the space requirements of multiple bonds compare to those of single bonds? | Multiple bonds usually require more space than single bonds. |

What does a polar covalent bond form between? | two atoms with different electronegativities |

A polar molecule is the result of what? | unequal distribution of charge caused by polar bonds and shape |

If a molecule is polar, then it has what? | a dipole moment |

What is the "Vector Addition Approach" to determine if a molecule is polar? | A molecule is nonpolar if its bond dipoles are symmetrically oriented such that they effectively cancel. |

What is the "Centers of Charge Approach" to determine if a molecule is polar? | A molecule is nonpolar if its centers of positive and negative charge coincide. |

What are the six perfectly symmetrical shapes? | linear, trigonal planar, tetrahedral, trigonal bipyramidal, octahedral, and square planar |

Are hydrocarbons polar or nonpolar? | nonpolar |

Perfectly symmetric molecules are ...? | nonpolar |

The main idea behind Valence Bond Theory is what? | Bonds form when singly-occupied atomic orbitals "overlap". |

Whenever the overlap of simple atomic orbitals does not adequately explain certain bond properties, | the concept of hybridization is invoked |

hybridization | the process in which orbitals are "mixed or combined" resulting in new hybrid orbitals |

To do Valence Bond Theory, what do you have to write? | electron configuration |

"mixing" one s and one p orbital results in | 2 sp orbitals |

"mixing" one s and two p orbitals results in | 3 sp^2 orbitals |

"mixing" one s and three p orbitals results in | 4 sp^3 orbitals |

"mixing" one s, three p, and one d orbital results in | 5 sp^3d orbitals |

"mixing" one s, three p, and two d orbitals results in | 6 sp^3d^2 orbitals |

a sigma bond occurs | when the electron density is concentrated symmetrically along the inter-nuclear axis |

a pi bond occurs | when the electron density is concentrated above and below but not on the inter-nuclear axis; when there are parallel p orbitals |

a single bond contains | one sigma bond |

a double bond contains | one sigma bond and one pi bond |

a triple bond contains | one sigma bond and two pi bonds |

Which is stronger: a sigma bond or a pi bond? | a sigma bond |

Why is a sigma bond stronger than a pi bond? | better overlap |