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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

so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
how to fabricate graphene ink ?
SUYASH Reply
for screen printed electrodes ?
SUYASH
What is lattice structure?
s. Reply
of graphene you mean?
Ebrahim
or in general
Ebrahim
in general
s.
Graphene has a hexagonal structure
tahir
On having this app for quite a bit time, Haven't realised there's a chat room in it.
Cied
what is biological synthesis of nanoparticles
Sanket Reply
what's the easiest and fastest way to the synthesize AgNP?
Damian Reply
China
Cied
types of nano material
abeetha Reply
I start with an easy one. carbon nanotubes woven into a long filament like a string
Porter
many many of nanotubes
Porter
what is the k.e before it land
Yasmin
what is the function of carbon nanotubes?
Cesar
I'm interested in nanotube
Uday
what is nanomaterials​ and their applications of sensors.
Ramkumar Reply
what is nano technology
Sravani Reply
what is system testing?
AMJAD
preparation of nanomaterial
Victor Reply
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
Himanshu Reply
good afternoon madam
AMJAD
what is system testing
AMJAD
what is the application of nanotechnology?
Stotaw
In this morden time nanotechnology used in many field . 1-Electronics-manufacturad IC ,RAM,MRAM,solar panel etc 2-Helth and Medical-Nanomedicine,Drug Dilivery for cancer treatment etc 3- Atomobile -MEMS, Coating on car etc. and may other field for details you can check at Google
Azam
anybody can imagine what will be happen after 100 years from now in nano tech world
Prasenjit
after 100 year this will be not nanotechnology maybe this technology name will be change . maybe aftet 100 year . we work on electron lable practically about its properties and behaviour by the different instruments
Azam
name doesn't matter , whatever it will be change... I'm taking about effect on circumstances of the microscopic world
Prasenjit
how hard could it be to apply nanotechnology against viral infections such HIV or Ebola?
Damian
silver nanoparticles could handle the job?
Damian
not now but maybe in future only AgNP maybe any other nanomaterials
Azam
Hello
Uday
I'm interested in Nanotube
Uday
this technology will not going on for the long time , so I'm thinking about femtotechnology 10^-15
Prasenjit
can nanotechnology change the direction of the face of the world
Prasenjit Reply
At high concentrations (>0.01 M), the relation between absorptivity coefficient and absorbance is no longer linear. This is due to the electrostatic interactions between the quantum dots in close proximity. If the concentration of the solution is high, another effect that is seen is the scattering of light from the large number of quantum dots. This assumption only works at low concentrations of the analyte. Presence of stray light.
Ali Reply
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
bamidele Reply
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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