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Properties of carbon-carbon bonds in two carbon atom molecules
Ethane Ethene Acetylene (Ethyne)
Bond strength (kJ/mol) 347 589 962
Bond length(pm) 154 134 120

Looking at the data, it is very clear that the bonding between the carbon atoms in these three molecules must be very different. The bond strength increases when there are fewer H atoms, and the bond length gets progressively shorter with fewer H atoms. These observations are reinforced by looking at carbon-carbonbond strengths and lengths in other C n H 2n+2 molecules, like propane and butane. In all of these molecules, the bond strengths and lengths are comparable to those in ethane.

The bond in ethene is about one and a half times stronger than the bond in ethane; this suggests that there might be a second bond between the two carbon atoms. This could be formed from the two unpaired and unshared electrons in the ethene structure above. Similarly, the bond in acetylene is about two and a half times stronger than the bond in ethane, so we can imagine that this results from the sharing of three pairs of electrons between the two carbon atoms. These assumptions produce the following Lewis structures:

These structures appear to make sense from two regards. First, these structures would explain the trend in carbon-carbon bond strengths as arising from the increasing number of shared pairs of electrons. Second, each carbon atom has a complete octet of electrons. Our model now reveals that there is a “double bond” in ethane and a “triple bond” in acetylene.

We thus extend our model of valence shell electron pair sharing to conclude that carbon atoms can bond by sharing one, two, or three pairs of electrons as needed to complete an octet of electrons, and that the strength of the bond is greater when more pairs of electrons are shared. Moreover, the data above tell us that the carbon-carbon bond in acetylene is shorter than that in ethene, which is shorter than that in ethane. We conclude that triple bonds are shorter than double bonds, which are shorter than single bonds.

Observation 5: hydrocarbon compounds containing nitrogen, oxygen, and the halogens

Many compounds composed primarily of carbon and hydrogen also contain some oxygen or nitrogen, or one or more of the halogens. These include the majority of biomolecules, such as amino acids and proteins. This means that it would be very desirable to extend our understanding of bonding by developing Lewis structures for these types of molecules.

Recall that a nitrogen atom has a valence of 3 and has five valence electrons. In our notation, we could draw a structure in which each of the five electrons appears separately in a ring, similar to what we drew for C. However, our new understanding of covalent bonding tells us that unpaired electrons on atoms are shared with other atoms to form bonds. Having all five valence electrons in an N atom unpaired would imply that an N atom would generally form five bonds to pair its five valence electrons. Since the valence is actually 3, our notation should have three unpaired electrons. One possibility looks like:

Questions & Answers

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 to know photocatalytic properties of tio2 nanoparticles...what to do now
Akash Reply
it is a goid question and i want to know the answer as well
characteristics of micro business
for teaching engĺish at school how nano technology help us
Do somebody tell me a best nano engineering book for beginners?
s. Reply
there is no specific books for beginners but there is book called principle of nanotechnology
what is fullerene does it is used to make bukky balls
Devang Reply
are you nano engineer ?
fullerene is a bucky ball aka Carbon 60 molecule. It was name by the architect Fuller. He design the geodesic dome. it resembles a soccer ball.
what is the actual application of fullerenes nowadays?
That is a great question Damian. best way to answer that question is to Google it. there are hundreds of applications for buck minister fullerenes, from medical to aerospace. you can also find plenty of research papers that will give you great detail on the potential applications of fullerenes.
what is the Synthesis, properties,and applications of carbon nano chemistry
Abhijith Reply
Mostly, they use nano carbon for electronics and for materials to be strengthened.
is Bucky paper clear?
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
so some one know about replacing silicon atom with phosphorous in semiconductors device?
s. Reply
Yeah, it is a pain to say the least. You basically have to heat the substarte up to around 1000 degrees celcius then pass phosphene gas over top of it, which is explosive and toxic by the way, under very low pressure.
Do you know which machine is used to that process?
how to fabricate graphene ink ?
for screen printed electrodes ?
What is lattice structure?
s. Reply
of graphene you mean?
or in general
in general
Graphene has a hexagonal structure
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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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