Book Cover Organic Chemistry 4e Carey
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Chapter 1: Chemical Bonding



Summary | Atoms, Electrons and Orbitals | Bond types: Ionic, Covalent, Polar Covalent | Lewis Structures and Formal Charge | The Shapes of Molecules | Hybridization | Self Assessment | Quiz |


Bond types: Ionic, Covalent, Polar Covalent

Chapter 1: Chemical Bonding

Bond types:

Why is it important to understand the structural arrangement of electrons in an atom?

In everyday life, chemistry arises out of the interaction of molecules with molecules... but what is a molecule? It is a collection of atoms.  When the atoms come together their electron clouds interact with one another and if this interaction is 'favorable' then bonding occurs.

One of the driving forces behind bonding is an atoms desire to obtain a stable valence electron configuration.   For the atoms that are most important in organic chemistry, (N, C, O, Cl, Br, and I),  this is an octet of electrons, which is similiar to the valence electron configuration of the nearest noble gas (ns2np6).

Ionic bonds result when electrons are tranfered between atoms.
Covalent bonds result when valence electrons are shared between atoms.

You should be able to identify whether an ionic or covalent bond is being formed between atoms.  Try some questions.  If you are having difficulty then you need to review bonding.

Most bonds within organic molecules will be covalent.  The execeptions will be compounds which possess metal atoms (where the metal atoms should be treated as ions).   It is important to note that the electron distribution within a covalent bond is not always symmetrical.  If it is not then the bond is said to be polar as opposed to non-polar.

If a bond is covalent you should be able to identify whether it is polar or non-polar.   Try some questions.  If you are having difficulty then you need to review bond polarity.

Bonds:

Ionic bonds result when electrons are tranfered between atoms.  The result is the formation of ions.   What is referred to as an ionic bond is really the, non-directional, electrostatic interaction between  ions.
General rule:  Ionic bonds are formed when the electronegativity difference (Dc) between the atoms is > 1.7.

Covalent bonds result when valence electrons are shared between atoms.  What is referred to as a covalent bond is a balance between the attractive and repulsive forces between the atoms which ends up placing electron density between the atoms.
General rule:  Covalent bonds are formed when the electronegativity difference (Dc) between the atoms is < 1.7

Are the electrons equally shared?  No.  It is important to note that unless Dc = 0, there is unequal sharing of the electrons.  This leads to a bond polarity.

Most bonds within organic molecules will be covalent.  The execeptions will be compounds which possess metal atoms (where the metal atoms should be treated as ions).

You should be able to identify whether an ionic or covalent bond is being formed between atoms.  If a bond is covalent you should be able to identify whether it is polar or non-polar.

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