University:
Purdue University
Course:
CHM 62100 | Advanced Analytical Chemistry
Academic year:

2019
Views:

295

Pages:

10
Author:

Hallie Randolph

Topic: Lewis structures, Covalent bonding and polarity Covalent Bonding • Covalent bonding is a chemical bond between two or more non-metals in a fixed ratio. • The covalent bond consist of two or more non metal atoms sharing their valence electrons with each other. The substance formed after a covalent bond is done is called a molecule because it consists of only non metals. Therefore the special name for covalent compounds are called molecules. Types of covalent bond Types of covalent bond continued • Single Bond- This is a covalent bond that consists of the sharing of 1 pair of valence electrons therefore has 2 electrons • Double Bond- This is a covalent bond that consists of the sharing of 2 pairs of valence electrons ons therefore has 4 electrons • Triple Bond- This is a covalent bond that consists of the sharing of 3 pairs of valence electrons and therefore has ons therefore has 6 electrons • Bond strength increases in the order: Single bond->double bond->triple bond Sigma bonds and pi bonds • Sigma and pi bonds are types of covalent bonds that differ in the overlapping of atomic orbitals. Covalent bonds are formed by the overlapping of atomic orbitals.. Parameters that govern sigma bond and pi bonds • Various bond parameters such as bond length, bond angle, and bond enthalpy depend on the way the overlapping of atomic orbital takes place. This overlap occurs in two major ways, giving rise to two primary types of covalent bonds, i.e. sigma and pi bonds Sigma (σ) Bond • Sigma bonds are a result of the head-to-head overlapping of atomic orbitals whereas pi bonds are formed by the lateral overlap of two atomic orbitals along the internuclear axis. Sigma bonds are the strongest covalent bonds, owing to the direct overlapping of the participating orbitals. The electrons participating in a σ bond are commonly referred to as σ electrons. Types of sigma bonds • s-s Overlapping • In this kind of overlapping, one ‘s’ orbital from each participating atom undergoes head-on overlapping along the internuclear axis. An s orbital must be halffilled before it overlaps with another. continued • The overlapping of two s orbitals resulting in a sigma bond is illustrated above. This type of overlap occurs in H2 molecules, where each hydrogen atom has a halffilled s orbital. s-p Overlapping • Here, one half filed s orbital overlaps with one half-filled p orbitals along the internuclear axis, forming a covalent bond. This condition is illustrated below. This type of overlapping can be observed in ammonia An NH3 molecule features 3 sigma bonds, formed by the overlap of the 2px, 2py, and 2pz orbitals belonging to the nitrogen atom and the 1s orbitals of the three hydrogen atoms.

Lewis Structures, Covalent Bonding and Polarity Lecture

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