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Note that this structure leaves three of the valence electrons “unpaired” and thus ready to join in a shared electron pair. The remaining two valence electrons are “paired,” and this notation implies that they therefore are not generally available for sharing in a covalent bond. This notation is consistent with the available data, i.e. five valence electrons and a valence of 3. Pairing the two non-bonding electrons seems reasonable in analogy to the fact that electrons are paired in forming covalent bonds.

We can draw similar structures for oxygen and fluorine. The other halogens will have structures like F, since they have the same valence and the same number of valence electrons.

With this notation in hand, we can now analyze structures for molecules including nitrogen, oxygen, and the halogens. The hydrides are the easiest:

Note that the octet rule is clearly obeyed for oxygen, nitrogen, and the halogens.

At this point, it becomes very helpful to adopt one new convention: a pair of bonded electrons will now be more easily represented in our Lewis structures by a straight line, rather than two dots. Double bonds and triple bonds are respectively represented by double and triple straight lines between atoms. We will continue to show non-bonded electron pairs explicitly with two dots.

For example, ethanol has the molecular formula C 2 H 6 O. The two carbon atoms are bonded together and the oxygen atom is attached to one of the two carbons; the hydrogen atoms are arranged to complete the valences of the carbon atoms and the oxygen atom:

In this structure, each line connecting two atoms represents a shared pair of electrons, or a covalent bond. The non-bonding pairs on oxygen are often called “lone pairs.” It is important for us to include them in our structure for three reasons. First, including the lone pairs helps us check that we have drawn a structure with the correct number of valence electrons. Let’s check this for this drawing. Each carbon atom contributes four valence electrons, the oxygen atom contributes six, and each hydrogen atom contributes 1. There are thus a total of 2(4)+6+6(1)=20 valence electrons. Counting electrons in the drawing, there are eight covalent bonds, each of which represents two valence electrons, and two lone pairs, for a total of 20 valence electrons.

Second, drawing the lone pairs helps us see that the octet rule is obeyed for the O atom. Third and perhaps most importantly, we will later learn that lone pairs of electrons are important in determining the physical and chemical properties of molecules.

Review and discussion questions

  1. Compounds with formulae of the form C n H 2n+2 are often referred to as "saturated" hydrocarbons.Using Lewis structures, explain how and in what sense these molecules are “saturated.”
  2. Molecules with formulae of the form C n H 2n+1 (e.g. CH 3 , C 2 H 5 ) are called "radicals" and are extremely reactive. UsingLewis structures, explain the reactivity of these molecules.
  3. State and explain the experimental evidence and reasoning which shows that multiple bonds are stronger and shorter than single bonds.
  4. Compare N 2 to H 4 N 2 . Predict which bond is stronger and explain why.

Questions & Answers

what is variations in raman spectra for nanomaterials
Jyoti Reply
I only see partial conversation and what's the question here!
Crow Reply
what about nanotechnology for water purification
RAW Reply
please someone correct me if I'm wrong but I think one can use nanoparticles, specially silver nanoparticles for water treatment.
yes that's correct
I think
what is the stm
Brian Reply
is there industrial application of fullrenes. What is the method to prepare fullrene on large scale.?
industrial application...? mmm I think on the medical side as drug carrier, but you should go deeper on your research, I may be wrong
How we are making nano material?
what is a peer
What is meant by 'nano scale'?
What is STMs full form?
scanning tunneling microscope
how nano science is used for hydrophobicity
Do u think that Graphene and Fullrene fiber can be used to make Air Plane body structure the lightest and strongest. Rafiq
what is differents between GO and RGO?
what is simplest way to understand the applications of nano robots used to detect the cancer affected cell of human body.? How this robot is carried to required site of body cell.? what will be the carrier material and how can be detected that correct delivery of drug is done Rafiq
what is Nano technology ?
Bob Reply
write examples of Nano molecule?
The nanotechnology is as new science, to scale nanometric
nanotechnology is the study, desing, synthesis, manipulation and application of materials and functional systems through control of matter at nanoscale
Is there any normative that regulates the use of silver nanoparticles?
Damian Reply
what king of growth are you checking .?
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
Stoney Reply
why we need to study biomolecules, molecular biology in nanotechnology?
Adin Reply
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
what school?
biomolecules are e building blocks of every organics and inorganic materials.
anyone know any internet site where one can find nanotechnology papers?
Damian Reply
sciencedirect big data base
Introduction about quantum dots in nanotechnology
Praveena Reply
what does nano mean?
Anassong Reply
nano basically means 10^(-9). nanometer is a unit to measure length.
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
Damian Reply
absolutely yes
how did you get the value of 2000N.What calculations are needed to arrive at it
Smarajit Reply
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Source:  OpenStax, Concept development studies in chemistry 2013. OpenStax CNX. Oct 07, 2013 Download for free at http://legacy.cnx.org/content/col11579/1.1
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