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We further assume the structure of the atom as a massive, positively charged nucleus, whose size is much smaller than that of the atom as a whole, surrounded by a vast open space in which negatively charged electrons move. These electrons can be effectively partitioned into a core and a valence shell, and it is only the electrons in the valence shell which are significant to the chemical properties of the atom. The number of valence electrons in each atom is equal to the group number of that element in the Periodic Table.

We will base much of our work on understanding the Periodic Law, which states that the chemical and physical properties of the elements are periodic functions of the atomic number. Finally, we will assume an understanding of Coulomb’s Law, which describes the attractions and repulsions amongst charged particles.

Observation 1: valence and the octet rule

To begin to understand chemical bonding, we will examine the valence of an atom, which is defined as the atom’s most common tendency to form bonds to other atoms. We can figure these out by looking at some common molecular formulae for molecules formed by each atom. We’ll start with the easiest case, the atoms of the noble gases. Since these atoms do not tend to combine with any other atoms, we will assign their valence as 0, meaning that these atoms tend to form 0 bonds. This doesn’t really get us very far.

To find the valence of an atom which does form bonds, let’s pick molecules which contain only a single atom of the type we’re interested in and see how many other atoms it can combine with. Oxygen is a good place to start. For example, a single O atom will combine with two H atoms to form the most common molecule H 2 O. Only under rare circumstances would we find any other combination of H and O in a neutral molecule. As such, it appears that the valence of an O atom is 2. Next we consider hydrogen, which combines with virtually any other element except the noble gases. Compounds containing hydrogen can contain a huge variety of the number of H atoms. However, molecules with a single H atom most typically contain only a single other atom, for example HF. A single C atom can combine with four H atoms, but a single H atom typically does not combine with more than one other atom. We do not typically see molecules like C 4 H. A conspicuous feature of molecules containing hydrogen is that there are typically many more hydrogen atoms than other atoms. For example, hydrogen in combination with carbon alone can form CH 4 , C 2 H 6 , C 8 H 18 , and many others. These observations lead us to conclude that an H atom has a valence of 1, meaning that a single H atom will typically only form 1 bond to another atom. This seems reasonable, since each H atom contains only a single proton and a single electron. This conclusion also is consistent with our conclusion that O atoms have a valence of 2, since the most common hydrogen-oxygen molecule is H 2 O.

We can use hydrogen’s valence of 1 to find the valence of other atoms. For example, the valence of C must be 4, since one C atom can combine with 4 H atoms, but not 5, and typically not 3. Nitrogen atoms have a valence of 3, to form NH 3 . Fluorine atoms have a valence of 1, to form HF molecules.

Questions & Answers

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
right! what he said ⤴⤴⤴
Tamia
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
kkk nice
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
im not good at math so would this help me
Rachael Reply
yes
Asali
I'm not good at math so would you help me
Samantha
what is the problem that i will help you to self with?
Asali
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
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
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 2013. OpenStax CNX. Oct 07, 2013 Download for free at http://legacy.cnx.org/content/col11579/1.1
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