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Not all triatomic molecules are bent, however. As a common example, C O 2 is a linear molecule. Larger polyatomics can have a variety of shapes, as illustrated in . Ammonia, N H 3 , is a pyramid-shaped molecule, with the hydrogens in an equilateraltriangle, the nitrogen above the plane of this triangle, and a H-N-H angle equal to 107°. The geometry of C H 4 is that of a tetrahedron, with all H-C-H angles equal to 109.5°. (See also .) Ethane, C 2 H 6 , has a geometry related to that of methane. The two carbons arebonded together, and each is bonded to three hydrogens. Each H-C-H angle is 109.5° and each H-C-C angle is109.5°. By contrast, in ethene, C 2 H 4 , each H-C-H bond angle is 116.6° and each H-C-C bond angle is121.7°. All six atoms of ethene lie in the same plane. Thus, ethene and ethane have very different geometries, despite thesimilarities in their molecular formulae.

Molecular structures

We begin our analysis of these geometries by noting that, in the molecules listed above which do not contain double or triple bonds ( H 2 O , N H 3 , C H 4 and C 2 H 6 ), the bond angles are very similar, each equal to or very close tothe tetrahedral angle 109.5°. To account for the observed angle, we begin with our valence shell electron pair sharing model,and we note that, in the Lewis structures of these molecules, the central atom in each bond angle of these molecules contains four pairsof valence shell electrons. For methane and ethane, these four electron pairs are all shared with adjacent bonded atoms, whereasin

ammonia or water, one or two (respectively) of the electron pairs are not shared with any other atom. Theseunshared electron pairs are called lone pairs . Notice that, in the two molecules with no lone pairs, all bond angles are exactly equal to the tetrahedral angle, whereas the bond angles are only close in the molecules with lonepairs

One way to understand this result is based on the mutual repulsion of the negative charges on the valence shellelectrons. Although the two electrons in each bonding pair must remain relatively close together in order to form the bond,different pairs of electrons should arrange themselves in such a way that the distances between the pairs are as large as possible.Focusing for the moment on methane, the four pairs of electrons must be equivalent to one another, since the four C-H bonds areequivalent, so we can assume that the electron pairs are all the same distance from the central carbon atom. How can we positionfour electron pairs at a fixed distance from the central atom but as far apart from one another as possible? A little reflectionreveals that this question is equivalent to asking how to place four points on the surface of a sphere spread out from each otheras far apart as possible. A bit of experimentation reveals that these four points must sit at the corners of a tetrahedron, anequilateral triangular pyramid, as may be seen in . If the carbon atom is at the center of this tetrahedron and the four electron pairs at placed atthe corners, then the hydrogen atoms also form a tetrahedron about the carbon. This is, as illustrated in , the correct geometry of a methane molecule. The angle formed by any two corners of a tetrahedron andthe central atom is 109.5°, exactly in agreement with the observed angle in methane. This model also works well in predictingthe bond angles in ethane.

Questions & Answers

how do they get the third part x = (32)5/4
kinnecy Reply
can someone help me with some logarithmic and exponential equations.
Jeffrey Reply
sure. what is your question?
ninjadapaul
20/(×-6^2)
Salomon
okay, so you have 6 raised to the power of 2. what is that part of your answer
ninjadapaul
I don't understand what the A with approx sign and the boxed x mean
ninjadapaul
it think it's written 20/(X-6)^2 so it's 20 divided by X-6 squared
Salomon
I'm not sure why it wrote it the other way
Salomon
I got X =-6
Salomon
ok. so take the square root of both sides, now you have plus or minus the square root of 20= x-6
ninjadapaul
oops. ignore that.
ninjadapaul
so you not have an equal sign anywhere in the original equation?
ninjadapaul
Commplementary angles
Idrissa Reply
hello
Sherica
im all ears I need to learn
Sherica
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Tamia
hii
Uday
what is a good calculator for all algebra; would a Casio fx 260 work with all algebra equations? please name the cheapest, thanks.
Kevin Reply
a perfect square v²+2v+_
Dearan Reply
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Abdirahman Reply
algebra 2 Inequalities:If equation 2 = 0 it is an open set?
Kim Reply
or infinite solutions?
Kim
The answer is neither. The function, 2 = 0 cannot exist. Hence, the function is undefined.
Al
y=10×
Embra Reply
if |A| not equal to 0 and order of A is n prove that adj (adj A = |A|
Nancy Reply
rolling four fair dice and getting an even number an all four dice
ramon Reply
Kristine 2*2*2=8
Bridget Reply
Differences Between Laspeyres and Paasche Indices
Emedobi Reply
No. 7x -4y is simplified from 4x + (3y + 3x) -7y
Mary Reply
is it 3×y ?
Joan Reply
J, combine like terms 7x-4y
Bridget Reply
how do you translate this in Algebraic Expressions
linda Reply
Need to simplify the expresin. 3/7 (x+y)-1/7 (x-1)=
Crystal Reply
. After 3 months on a diet, Lisa had lost 12% of her original weight. She lost 21 pounds. What was Lisa's original weight?
Chris 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. OpenStax CNX. Dec 06, 2007 Download for free at http://cnx.org/content/col10264/1.5
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