Molecular geometry and hybridization

What is the tetrahedral bond angle?

109.5 degrees

What is the angle of the bonds in a pure tetrahedral arrangement?

109.5°

What angle does a trigonal planar carbon have?

120°

Linear (simple)

2 bonding Domains, 0 non-bonding

Bent (107°)

2 bonding domains, 1 non-bonding

Bent (<104.5°)

2 bonding domains, 2 non-bonding

Linear (complex)

2 bonding domains, 3 non-bonding

Trigonal Planar

3 bonding bomains, 0 non-bonding, 120

Trigonal Pyramidal

3 bonding domains, 1 non-bonding, 107°

T-shaped

3 bonding domains, 2 non-bonding, 90°

Tetrahedral

4 bonding domains, 0 non-bonding, 109.5°

See-Saw

4 bonding domains, 1 non-bonding, 90°

How many orbitals are hybridized in sp3 hybridization?

4 orbitals

Trigonal Bipyramidal

5 bonding domains, 0 non-bonding

Square Pyramidal

5 bonding domains, 1 non-bonding, 90°

Octahedral

6 bonding domains, 0 non-bonding, 90°

Valence Bond Theory (VB) / Hybridization

A bond is formed by the overlap of an orbital from 1 atom with an orbital from another atoms; allows for the mixing of orbitals and hybridization to fit the shape and energies observed in the molecule

Which of the following compounds is polar? A. NH₃ B. Br₂ C. CH₄ D. CO₂

A. NH₃

Which of the following molecules has a bent shape: A. NH₃ B. OF₂ C. CO₂ D. Cl₂CO

B

<107°, sp²

Bond angle and hybridization of bent (3 total domains)

104.5°, sp³

Bond angle and hybridization of bent (4 total domains)

180°, sp

Bond angle and hybridization of linear (simple)

107°, sp³

Bond angle and hybridization of pyramidal

109.5°, sp³

Bond angle and hybridization of tetrahedral

120°, sp²

Bond angle and hybridization of trigonal planar

120° in plane, 90° out of plane

Bond angle of trigonal bipyramidal

Bond Polarity and Molecular Polarity

Bond polarity can be determined by examining difference in electronegativity for the 2 atoms in the bond Molecular Polarity is the sum of the bonds in the molecule

How are C-H bonds formed?

By an overlap of sp3 orbital of Carbon and S orbital of Hydrogen

Which is stronger? C-C Sigma or C-H Sigma?

C-H > C-C

Valence Shell Electron Repulsion

Electron pairs move as far away as possible to minimize repulsive forces which determines the shape

Trigonal Bi-pyramidal and Octahedral electron and molecular geometries

For region of 5, take off from where there are three first 5 regions = makes angles of 120 (middle ones) and 90 (top and bottom) For region of 6, take off top and bottom (makes angles of 90)

Explain bonds in CH3+

Forms covalent bonds using sp2 orbitals. Unhybridized p orbitals remain empty

How are sp2 orbitals hybridized?

From an s orbital and two of the p orbitals

Rank Hydrogen-Halogen Bond strengths?

H-F > H-Cl > H-Br > H-I

how do you know when something is polar?

If the molecule has a net dipole, then it is polar; if the structure is symmetric, then it is non-polar; if it is linear or square planar, then it is non-polar (this rule is more important than rule 1, so it overrules); if it has different terminal atoms, then it is polar (this rule overrules rule 1 and 2 because it is more important.)

contrast localized electron (aka hybridization) theory and molecular orbital theory

LE: localized, limited to 6 electron pairs, designed to fit the facts so hasn't undergone scientific method, easier. MO theory: delocalized, orbitals are not on one atom they are shared through out the molecule, based on scientific method and works all the time

To determine hybridization of an element?

Look at the Pi bonds: No Pi Bonds = sp3 hybridized 1 Pi Bond = sp2 hybridized 2 Pi Bonds = sp hybridized *Exceptions are carbocations and carbon radicals because they have an empty or 1/2 filled p orbital

Dipole Moment

Measure of the polarity of the molecule Defined as product of the magnitude of the partial charges δ+ and δ- and the distance (d) seperating these charges

Explain bonds in Methyl Anion (-CH3)

Methyl Anion has 3 pairs of bonding electrons and 1 lone pair. It is sp3 hybridized

Which is weaker? Pi Bond or Sigma bond?

Pi Bond is weaker

T or F. According to the valence bond theory, side-by-side bonds are termed pi (π) bonds

T

How are sp orbitals hybridized?

To minimize electron repulsion, two sp orbitals will point in the opposite direction

Shorter bonds are stronger bonds?

True

in the localized electron model electron pairs are located ___________ ______ _______, but the orbitals around the central atom are ________

around specific atoms; modified

Predict the shape of OCl₂

bent

Predict the shape of O₃

bent

Which of the following shapes is always polar? linear, tetrahedral, bent, trigonal planar

bent

compare molecular and hybrid orbitals

both consist of atomic and hybrid orbitals, use localized theory, hold two electrons, and shrodinger's equation holds

how are molecular orbitals and atomic orbitals similar?

both hold two electrons, form pi bonds, and shrodinger's equation holds. (longer description - Atomic orbitals describe the probable locations of electrons in solitary atoms. The most familiar atomic orbitals are s, p, d, and f. Molecular orbitals describe the probable locations of electrons in molecules (compounds made of multiple atoms). Both atomic and molecular orbitals are filled by two electrons of opposite spin. Atomic orbitals "mix" to form molecular orbitals. In chemistry, molecular orbitals broadly fall into sigma and pi classes. They are also divided into bonding, non-bonding, and antibonding orbitals.)

compare localized electron theory and molecular orbital theory

both theories explain covalent bonding

The symbols δ⁻ and δ⁺ represent the partial ___________ of a polar molecule

charges

definition of hybridization

combination of atomic orbitals of different energy to make a new set of orbitals of a different energy

the vector sum of all bond polarities that exist in a molecule is known as a

dipole moment

A double bond consists of a sigma bond (using ______ orbitals) and a pi bond (using ___ orbitals)

hybrid; p

The process by which new kinds of orbitals of equal energy are formed from a combination of orbitals of different energies is known as

hybridization

sp

hybridization of linear

sp³d²

hybridization of octahedral

sp³

hybridization of tetrahedral

sp³d

hybridization of trigonal bipyramidal

sp²

hybridization of trigonal planar

how are hybrid and atomic orbitals the same? how are they different?

in both, electrons remain on atoms; hybrid cannot be used in pi bonding while atomic can

how are molecular orbitals different than atomic orbitals?

in molecular orbitals the electrons go everywhere while in atomic orbitals the electrons are localized; molecular orbitals are made up of atomic orbitals;

Given the lewis structure for HCN, tell its shape and indicate the direction of the dipole moment if present

linear

Predict the shape of HCN

linear

Predict the shape of HF

linear

2 electron regions, 0 lone pair

linear, 180°

What more recent theory predicts the magnetic qualities of diatomic oxygen

molecular orbital theory

6 electron regions, 0 lone pair

octahedral, 90°

The presence of unpaired electrons in molecular orbitals has been associated with what phenomenon?

paramagnetism

What type of bond forms as a result of orbitals overlapping end to end?

sigma

Which is closer to the nucleus, sp2 or sp3 orbital?

sp2 orbital is closer

Is a C-H bond formed by sp2-s stronger than a sp3-s bond

sp2-s bond is stronger

Which is stronger? sp2-sp2 or sp3-sp3

sp2-sp2 < sp3-sp3

How is NH3 hybridized?

sp3

What hybridization do central Oxygens have?

sp3 (because they make four bonds)

How do you recognize an sp3 atom?

sp3 atoms make 4 bonds; Bond angles = 109.5 degrees

Predict the shape of CF₂Cl₂

tetrahedral (109.5°)

4 electron regions, 0 lone pair

tetrahedral, 109.5°

What determines the polarity of a polar bond?

the difference in electronegativity of the two elements

how are molecular and atomic and hybridized orbitals the same?

they all hold two electrons; Shrodinger's equation holds (the square of the wave function = probability)

similarities between Localized Electron (LE) Model and Molecular Orbital (MO) Model

they both describe covalent molecular and ionic structure and shape

name shapes in order of: sp3d, sp3, sp, sp2, sp3d2

triangular bipyramidal (5 regions); tetrahedral (4 regions); linear (2 regions with 2 unhybridized p's); triangular planar (5 regions w/ 1 unhybridized p); octrahedral (6)

5 electron regions, 0 lone pair

trigonal bipyramidal, 120° and 90°

Predict the shape of CH₂O

trigonal planar (120°)

3 electron regions, 0 lone pair

trigonal planar, 120°

Predict the shape of PH₃

trigonal pyramidal

The assumption that molecular shapes are largely determined by the repulsion of regions of electron concentration is known as the

valence shell electron pair repulsion, or VSEPR theory

octahedral, 90°

...