# 0.4 Covalent bonding and electron pair sharing

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## Foundation

We begin with our understanding of the relationship between chemical behavior and atomic structure. Thatis, we assume the Periodic Law that the chemical and physical properties of the elements are periodic functions of atomic number.We further assume the structure of the atom as a massive, positively charged nucleus, whose size is much smaller than that ofthe atom as a whole, surrounded by a vast open space in which move negatively charged electrons. These electrons can be effectivelypartitioned into a core and a valence shell, and it is only the electrons in the valence shell which are significant to thechemical properties of the atom. The number of valence electrons in each atom is equal to the group number of that element in thePeriodic Table.

## Goals

The atomic molecular theory is extremely useful in explaining what it means to form a compound its componentelements. That is, a compound consists of identical molecules, each comprised of the atoms of the component elements in a simple wholenumber ratio. However, the atomic molecular theory also opens up a wide range of new questions. We would like to know what atomicproperties determine the number of atoms of each type which combine to form stable compounds. Why are some combinations observed andother combinations not observed? Some elements with very dissimilar atomic masses (for example, iodine and chlorine) form very similarchemical compounds, but other elements with very similar atomic masses (for example, oxygen and nitrogen) form very dissimilarcompounds. What factors are responsible for the bonding properties of the elements in a similar group? In general, we need to knowwhat forces hold atoms together in forming a molecule.

We have developed a detail understanding of the structure of the atom. Our task now is to apply thisunderstanding to develop a similar level of detail about how atoms bond together to form molecules.

## Observation 1: valence and the periodic table

To begin our analysis of chemical bonding, we define the valence of an atom by its tendencies to form molecules. The inert gases do not tend to combine with any other atoms. Wethus assign their valence as 0, meaning that these atoms tend to form 0bonds. Each halogen prefers to form molecules by combining with a single hydrogen atom ( e.g. $HF$ , $H\mathrm{Cl}$ ). We thus assign their valence as 1, also taking hydrogen to alsohave a valence of 1. What we mean by a valence of 1 is that these atoms prefer to bind to only one other atom. The valence of oxygen,sulfur, etc. is assigned as 2, since two hydrogens are required to satisfy bonding needs of these atoms. Nitrogen, phosphorus, etc.have a valence of 3, and carbon and silicon have a valence of 4. This concept also applies to elements just following the inertgases. Lithium, sodium, potassium, and rubidium bind with a single halogen atom. Therefore, they also have a valence of 1.Correspondingly, it is not surprising to find that, for example, the combination of two potassium atoms with a single oxygen atomforms a stable molecule, since oxygen's valence of 2 is be satisfied by the two alkali atoms, each with valence 1. We canproceed in this manner to assign a valence to each element, by simply determining the number of atoms to which thiselement's atoms prefer to bind.

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
Difference between extinct and extici spicies
While the American heart association suggests that meditation might be used in conjunction with more traditional treatments as a way to manage hypertension
Researchers demonstrated that the hippocampus functions in memory processing by creating lesions in the hippocampi of rats, which resulted in ________.
The formulation of new memories is sometimes called ________, and the process of bringing up old memories is called ________.
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