5.1 Lewis structures

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Lewis notation and molecular structure

Although we have used diagrams to show the structure of molecules, there are other forms of notation that can be used, such as Lewis notation and Couper notation . Lewis notation uses dots and crosses to represent the valence electrons on different atoms. The chemical symbol of the element is used to represent the nucleus and the core electrons of the atom.

So, for example, a hydrogen atom would be represented like this:

A chlorine atom would look like this:

A molecule of hydrogen chloride would be shown like this:

The dot and cross in between the two atoms, represent the pair of electrons that are shared in the covalent bond.

Represent the molecule $\mathrm{H}{}_{2}\mathrm{O}$ using Lewis notation

1. The electron configuration of hydrogen is $1\mathrm{s}{}^{1}$ and the electron configuration for oxygen is $1\mathrm{s}{}^{2}2\mathrm{s}{}^{2}2\mathrm{p}{}^{4}$ . Each hydrogen atom has one valence electron, which is unpaired, and the oxygen atom has six valence electrons with two unpaired.

2. The water molecule is represented below.

Represent the molecule $\mathrm{HCN}$ (hydrogen cyanide) using Lewis notation

1. The electron configuration of hydrogen is $1\mathrm{s}{}^{1}$ , the electron configuration of nitrogen is $1\mathrm{s}{}^{2}2\mathrm{s}{}^{2}2\mathrm{p}{}^{3}$ and for carbon is $1\mathrm{s}{}^{2}2\mathrm{s}{}^{2}2\mathrm{p}{}^{2}$ . This means that hydrogen has one valence electron which is unpaired, carbon has four valence electrons, all of which are unpaired, and nitrogen has five valence electrons, three of which are unpaired.

2. The $\mathrm{HCN}$ molecule is represented below. Notice the three electron pairs between the nitrogen and carbon atom. Because these three covalent bonds are between the same two atoms, this is a triple bond.

Represent the molecule $\mathrm{H}{}_{2}\mathrm{S}$ (hydrogen sulphide) using Lewis notation

1. Hydrogen has an electron configuration of $1\mathrm{s}{}^{1}$ and sulphur has an electron configuration of $1\mathrm{s}{}^{2}2\mathrm{s}{}^{2}2{p}{}^{6}3\mathrm{s}{}^{2}3\mathrm{p}{}^{4}$ . Each hydrogen atom has one valence electron which is unpaired, and sulphur has six valence electrons. Although sulphur has a variable valency, we know that the sulphur will be able to form 2 bonds with the hydrogen atoms. In this case, the valency of sulphur must be two.

2. The $\mathrm{H}{}_{2}\mathrm{S}$ molecule is represented below.

Another way of representing molecules is using Couper notation . In this case, only the electrons that are involved in the bond between the atoms are shown. A line is used for each covalent bond. Using Couper notation, a molecule of water and a molecule of $\mathrm{HCN}$ would be represented as shown in figures [link] and [link] below.

Atomic bonding and lewis notation

1. Represent each of the following atoms using Lewis notation:
1. beryllium
2. calcium
3. lithium
2. Represent each of the following molecules using Lewis notation:
1. bromine gas ( $\mathrm{Br}{}_{2}$ )
2. carbon dioxide ( $\mathrm{CO}{}_{2}$ )
3. Which of the two molecules listed above contains a double bond?
4. Two chemical reactions are described below.
• nitrogen and hydrogen react to form $\mathrm{NH}{}_{3}$
• carbon and hydrogen bond to form a molecule of $\mathrm{CH}{}_{4}$
For each reaction, give:
1. the valency of each of the atoms involved in the reaction
2. the Lewis structure of the product that is formed
3. the chemical formula of the product
4. the name of the product
5. A chemical compound has the following Lewis notation:
1. How many valence electrons does element $\mathrm{Y}$ have?
2. What is the valency of element $\mathrm{Y}$ ?
3. What is the valency of element $\mathrm{X}$ ?
4. How many covalent bonds are in the molecule?
5. Suggest a name for the elements $\mathrm{X}$ and $\mathrm{Y}$ .

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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
what is biological synthesis of nanoparticles
what's the easiest and fastest way to the synthesize AgNP?
China
Cied
types of nano material
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.
what is nano technology
what is system testing?
preparation of nanomaterial
Yes, Nanotechnology has a very fast field of applications and their is always something new to do with it...
what is system testing
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
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.
the Beer law works very well for dilute solutions but fails for very high concentrations. why?
how did you get the value of 2000N.What calculations are needed to arrive at it
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The fundamental frequency of a sonometer wire streached by a load of relative density 's'are n¹ and n² when the load is in air and completly immersed in water respectively then the lation n²/na is
Properties of longitudinal waves