CHM 101: Hybridization and Shapes of Molecules

Podcast

Play an AI-generated podcast conversation about this lesson

Questions and Answers

How many 1s electrons does each atom provide in covalent bonding?

1 (correct)

What type of orbital hybridization occurs for the carbon atom in methane?

sp4

dsp3

sp2 (correct)

What is the geometry of the four C-H bonds in methane?

Tetrahedral (correct)

Octahedral

Linear

Trigonal planar

How many valence orbitals of carbon combine to form the sp3 hybrid orbitals?

4 Signup and view all the answers

What is the shape of the sp3 hybrid orbitals in methane?

Oblong Signup and view all the answers

What is the angle between any two orbitals in methane?

$109.5^\circ$ Signup and view all the answers

What is the most common bond angle for a molecule of ammonia (NH3)?

107.3˚ Signup and view all the answers

In methane (CH4), what type of hybridization does carbon exhibit?

sp3 Signup and view all the answers

The solid wedge in structural formulas represents a bond that is:

Meant to be pictured emerging from the page Signup and view all the answers

What is the approximate bond angle for a water molecule (H2O)?

104.5˚ Signup and view all the answers

How many nonbonding lone pairs does an oxygen atom in a water molecule (H2O) have?

2 Signup and view all the answers

What orbital type do the nitrogen-hydrogen (N-H) bonds in ammonia (NH3) form?

1s orbital in nitrogen and 1s orbital in hydrogen Signup and view all the answers

What is the hybridization of the carbon atoms in ethene?

sp2 Signup and view all the answers

What is the approximate bond angle in the ethene molecule?

120 o Signup and view all the answers

What is the length of the C-C bond in ethene?

1.34 Å Signup and view all the answers

What type of orbital remains unhybridized in ethene?

2pz Signup and view all the answers

What is the shape of the ethene molecule?

Planar (flat) Signup and view all the answers

What type of bond is formed by the direct overlap of valence orbitals?

Sigma bond Signup and view all the answers

Which type of bond is usually represented by a single line in structural formulas?

Sigma bond Signup and view all the answers

Which molecule is used to explain the concept of sigma bonds in the text?

Hydrogen (H2) Signup and view all the answers

Which of the following is not a learning objective related to the VSEPR theory?

Determining the number of lone pairs in a molecule Signup and view all the answers

Which of the following molecules is not used as an example for understanding hybridization and shapes of molecules?

SO2 Signup and view all the answers

What is the main principle used in predicting and interpreting the shapes/geometry of simple molecules and ions?

Valence shell electron pair repulsion (VSEPR) theory Signup and view all the answers

Study Notes

Covalent Bonding

Each atom provides a 1s electron, which is used in covalent bonding through the overlap of the two 1s orbitals, forming a pair within the two overlapping orbitals.
The two electrons form a strong bond due to the strong attraction they experience to the positive nuclei of the atoms.

Methane (CH4)

The simplest organic molecule.
Carbon has an electron configuration of 1s2, 2s2, 2px1, 2py1, 2pz.
Orbital hybridization takes place, where the four valence orbitals of the carbon combine to form four equivalent hybrid sp3 orbitals.
Each of the four valence electrons on the carbon occupies a single sp3 orbital.
The four C-H bonds in methane are arranged with tetrahedral geometry about the central carbon, with each bond having the same length and strength.
The sp3 hybrid orbitals are oblong in shape, with two lobes of opposite sign but different sizes.
The bigger lobes are directed towards the four corners of a tetrahedron, making the angle between any two orbitals in methane 109.5°.

Hybridization and Shapes of Molecules

Learning objectives:
- Understand sigma and pi bonds, and examples of simple molecules having them.
- Understand sp2, and sp3 orbital hybridization with specific examples.
- Understand the principles of the valence shell electron pair repulsion (VSEPR) theory.
- Understand the concept of bond angle.

Sigma (σ) Bonds

Sigma bonds are the strongest type of covalent bonds due to the direct overlap of valence orbitals.
The electrons in these bonds are sometimes referred to as sigma electrons.
A single bond is usually a sigma bond.

One Hydrogen (H2)

The simplest molecule to use to explain sigma bonds.
The bond is formed from the overlap between a half-filled 1s orbital in a hydrogen atom and a sp3 hybrid orbital in the central carbon.

The Solid Dash/Wedge System

A conventional way of drawing 2-dimensional structures of molecules.
Solid wedges represent bonds that are meant to be pictured emerging from the plane of the page.
Dashed wedges represent bonds that are meant to be pictured pointing into, or behind, the plane of the page.
Normal lines imply bonds that lie in the plane of the page.

Ammonia (NH3)

Nitrogen is sp3 hybridized.
The bonding arrangement is also tetrahedral, where the three N-H bonds of ammonia form the base of a trigonal pyramid.
The lone pair forms the top of the pyramid, and its slightly greater repulsive effect pushes the three N-H bonds away from the top of the pyramid, making the H-N-H bond angles not tetrahedral at 107.3°.

Water (H2O)

The overlap of sp3 hybrid orbitals on oxygen with 1s orbitals on the two hydrogen atoms makes the bonding in water occur.
The two non-bonding lone pairs on oxygen would be located in sp3 orbitals.
A molecule of water is ‘bent’ at an angle of approximately 104.5° (explained by VSEPR).

pi (π) Bonds

sp2 hybridization occurs in double-bonded compounds like ethene.

Ethene (C2H2)

Valence bond theory, and the hybrid orbital concept, describes bonding in double-bonded compounds like ethene.
The 2s, 2px, and 2py orbitals combine to form three sp2 hybrid orbitals, leaving the 2pz orbital unhybridized.
Characteristics of the ethene molecule relating to its bonding:
- It is a planar (flat) molecule.
- Bond angles are approximately 120°, and the C-C bond length is 1.34 Å, significantly shorter than the 1.54 Å single carbon-carbon bond in ethane.
- There is no rotation about the carbon-carbon double bond.

Studying That Suits You

Use AI to generate personalized quizzes and flashcards to suit your learning preferences.

Description

Test your knowledge on sigma and pi bonds, sp2 and sp3 orbital hybridization, and the VSEPR theory for predicting molecular shapes. Dive deep into the concepts taught by Dr. Olubunmi A. Adewusi at Lagos State University.