# 0.5 Molecular geometry and electron domain theory

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## Foundation

We begin by assuming a Lewis structure model for chemical bonding based on valence shell electron pair sharing and the octet rule. We thusassume the nuclear structure of the atom, and we further assume the existence of a valence shell of electrons in each atom whichdominates the chemical behavior of that atom. A covalent chemical bond is formed when the two bonded atoms share a pair of valenceshell electrons between them. In general, atoms of Groups IV through VII bond so as to complete an octet of valence shellelectrons. A number of atoms, including C, N, O, P, and S, can form double or triple bonds as needed to complete an octet. We know thatdouble bonds are generally stronger and have shorter lengths than single bonds, and triple bonds are stronger and shorter than doublebonds.

## Goals

We should expect that the properties of molecules, and correspondingly the substances which they comprise,should depend on the details of the structure and bonding in these molecules. The relationship between bonding, structure, andproperties is comparatively simple in diatomic molecules, which contain two atoms only, e.g. $H\mathrm{Cl}$ or ${O}_{2}$ . A polyatomic molecule contains more than two atoms. An example of the complexities which arise with polyatomic moleculesis molecular geometry: how are the atoms in the molecule arranged with respect to one another? In a diatomic molecule, only a singlemolecular geometry is possible since the two atoms must lie on a line. However, with a triatomic molecule (three atoms), there aretwo possible geometries: the atoms may lie on a line, producing a linear molecule, or not, producing a bent molecule. In moleculeswith more than three atoms, there are many more possible geometries. What geometries are actually observed? What determineswhich geometry will be observed in a particular molecule? We seek a model which allows us to understand the observed geometries ofmolecules and thus to predict these geometries.

Once we have developed an understanding of the relationship between molecular structure and chemical bonding, wecan attempt an understanding of the relationship of he structure and bonding in a polyatomic molecule to the physical and chemicalproperties we observe for those molecules.

## Observation 1: geometries of molecules

The geometry of a molecule includes a description of the arrangements of the atoms in the molecule. At asimple level, the molecular structure tells us which atoms are bonded to which. At a more detailed level, the geometry includesthe lengths of all of these bonds, that is, the distances between the atoms which are bonded together, and the angles between pairsof bonds. For example, we find that in water, ${H}_{2}O$ , the two hydrogens are bonded to the oxygen and each O-H bond lengthis 95.72pm (where $1\mathrm{pm}=10^{-12}m$ ). Furthermore, ${H}_{2}O$ is a bent molecule, with the H-O-H angle equal to 104.5°. (The measurement of these geometric properties is difficult,involving the measurement of the frequencies at which the molecule rotates in the gas phase. In molecules in crystalline form, thegeometry of the molecule is revealed by irradiating the crystal with x-rays and analyzing the patterns formed as the x-raysdiffract off of the crystal.)

Is there any normative that regulates the use of silver nanoparticles?
what king of growth are you checking .?
Renato
What fields keep nano created devices from performing or assimulating ? Magnetic fields ? Are do they assimilate ?
why we need to study biomolecules, molecular biology in nanotechnology?
?
Kyle
yes I'm doing my masters in nanotechnology, we are being studying all these domains as well..
why?
what school?
Kyle
biomolecules are e building blocks of every organics and inorganic materials.
Joe
anyone know any internet site where one can find nanotechnology papers?
research.net
kanaga
sciencedirect big data base
Ernesto
Introduction about quantum dots in nanotechnology
what does nano mean?
nano basically means 10^(-9). nanometer is a unit to measure length.
Bharti
do you think it's worthwhile in the long term to study the effects and possibilities of nanotechnology on viral treatment?
absolutely yes
Daniel
how to know photocatalytic properties of tio2 nanoparticles...what to do now
it is a goid question and i want to know the answer as well
Maciej
Abigail
for teaching engĺish at school how nano technology help us
Anassong
Do somebody tell me a best nano engineering book for beginners?
there is no specific books for beginners but there is book called principle of nanotechnology
NANO
what is fullerene does it is used to make bukky balls
are you nano engineer ?
s.
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.
Tarell
what is the actual application of fullerenes nowadays?
Damian
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.
Tarell
what is the Synthesis, properties,and applications of carbon nano chemistry
Mostly, they use nano carbon for electronics and for materials to be strengthened.
Virgil
is Bucky paper clear?
CYNTHIA
carbon nanotubes has various application in fuel cells membrane, current research on cancer drug,and in electronics MEMS and NEMS etc
NANO
so some one know about replacing silicon atom with phosphorous in semiconductors device?
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.
Harper
Do you know which machine is used to that process?
s.
how to fabricate graphene ink ?
for screen printed electrodes ?
SUYASH
What is lattice structure?
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
how did you get the value of 2000N.What calculations are needed to arrive at it
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