Simple Procedure for Writing Lewis Structures

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Simple Procedure for writing Lewis Structures Lewis Structures for nitric

acid (HNO3)

Lewis Electron Dot Structure of

nitric acid HNO3A simple procedurefor writing Lewis Structureswas given in a previousarticle entitled Lewis Structures and the Octet Rule.Several workedexamples relevant to this procedure were given in previous posts please seethe Sitemap - Table of Contents Lewis Electron Dot Structures!.

Let us consider the case of nitric acid HNO3.

Nitric acidis a strong o"idi#in$ a$entand it dissolves practically all metalsexcept gold and platinum and some other precious metals. As such, is an

important raw material for the chemical and pharmaceutical industr%. tis mainly used for etching and for the production of pure nitrates. !venthough nitric acid was known since the "th century # alchemists used it toseparate gold and silver # its mass production started in $"%& when a'erman chemist (ilhelm )stwald developed an industrial process. *he'erman corporation&'S(start producing it in an industrial scale +y $"$.nitially it was used for the production of explosives +ut today its main use isfor the production of fertili#erssuch as ammonium nitrate. )ther mainapplications is for the production of explosives, n%lon precursors andsubstituted or$anic compounds.

n elemental anal%sis +yatomic a+sorption spectroscopy, )C*, graphitefurnace atomic spectroscopy dilute nitric acid is used as a -solvent- for thedetermination of metal traces in solution.

Step +, The central atom will be the N atom since it is the lesselectrone$atie H is a terminal atom . it cannot be a central atom!/Connect the atoms with sin$le bonds,

Step 0, Calculate the 1 of electrons in 2 bonds multiple bonds!usin$ formula +!,
http://chem-net.blogspot.com/2011/05/lewis-structures-and-octet-rule-simple.htmlhttp://chem-net.blogspot.com/2011/05/lewis-structures-and-octet-rule-simple.htmlhttp://chem-net.blogspot.com/2011/05/lewis-structures-and-octet-rule-simple.htmlhttp://chem-net.blogspot.gr/p/table.htmlhttp://www.epa.gov/ttnchie1/ap42/ch08/final/c08s08.pdfhttp://chem-net.blogspot.com/2013/08/atomic-absorption-spectrometry.htmlhttp://chem-net.blogspot.com/2013/09/sampling-techniques-atomic-absorption.htmlhttp://chem-net.blogspot.com/2013/09/sampling-techniques-atomic-absorption.htmlhttp://chem-net.blogspot.com/2011/05/lewis-structures-and-octet-rule-simple.htmlhttp://chem-net.blogspot.gr/p/table.htmlhttp://www.epa.gov/ttnchie1/ap42/ch08/final/c08s08.pdfhttp://chem-net.blogspot.com/2013/08/atomic-absorption-spectrometry.htmlhttp://chem-net.blogspot.com/2013/09/sampling-techniques-atomic-absorption.htmlhttp://chem-net.blogspot.com/2013/09/sampling-techniques-atomic-absorption.htmlhttp://chem-net.blogspot.com/2011/05/lewis-structures-and-octet-rule-simple.htmlhttp://chem-net.blogspot.com/2011/05/lewis-structures-and-octet-rule-simple.html


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(here n in this case is since /N)0consists of 1ve atoms +ut one of them isa / atom.

(here 2 3 4$ 5 6 5 5 6 5 67 3 &

*herefore, 8 3 6n 5 & 9 2 3 6 : 5 & 9 & 3 & So there are 0 2 electronsinHNO3

+ double bond must be added to the structure of Step +/

Step 3 4, One double bond must therefore be placed throu$h the3 N-O bonds/ Therefore5 the Lewis resonance structures for HNO3are as follows,


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CHEMC!L "ON#N$ !N# COMPO%N#

&O'M!ONOne of the most important requirements in chemistry is to become familiar with the ways in

which elements react to form compounds. We will investigate the types of chemical bonds, waysto predict compositions and the conventions of naming the compounds.

;hemical +onds make atoms more sta+le than they are if non#+onded


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!he inference we draw from this is that the atom wants to obtain a filled shell, and this it

achieves by forming bonds. !his can be done by either addition of electrons or removal of

electrons. !he noble gas atom already has a filled shell and does not need to indulge in bonding

to achieve it.

Elements on the left side of the table, metals, will lose electrons to form positive ions* elements

on the right hand side of the table, nonmetals, will gain electrons. (n both cases, a filled shell

will result.

Of course, we must recogni-e that the atom is now charged because the electron and proton

counts are not equal. Electron loss creates positive ions, and electron gain creates negative ions.


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(n an ionic compound, a positive ion and a negative ion come together and form an ionic bond

through the strong electrostatic interaction between the ions of opposing charge.

*redictin$ ion char$es

(t is essential to be able to predict the charge on an ion in order to predict the composition of

compounds formed containing it. We can use the periodic table to assist us in this.

!he table shows the periodic table with the charges of the ions shown. +ote, that in this version,

the ( scheme of " / ") is used rather than the older "A / )A. We find a very strong

correspondence between group number 0using the older scheme1 and ion charge.

Rule to predict ion char$e

;ation

;harge 3 group num+er

Anion

;harge 3 #4= # group num+er7


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)onic compounds

(onic compounds alwayscontain a metal and a nonmetal.

*redictin$ composition

A compound is always neutral, and so charges of the ions in the compound must balance out. We

always%'&know the charges on the ions from the periodic table. o the net stage is to determine

the correct ratio of ions that will produce charge neutrality. 2asically the total number of positive

charges must equal the total number of negative charges. !he document 3!ype " #ompounds4

provides guidance in this.

Elements with ariable ionic char$eWe have shown that the periodic table can be used to predict ionic charges. 5owever, there are

some elements that are not susceptible to this approach. ome of the heavier Atype elements

like tin and lead show two ionic charge possibilities6 n$7and n87* 9b$7and 9b87. (n writing the

formula we would identify the state by writing n0((1 or n0(:1.

!he transition metals also show a high degree of variable ionic charges6 #r$7, #r'7, #r87, Fe$7,

Fe'7, #u7, #u$7and so on. ;ou are not epected to remember all of these different ions, but be

able to predict a composition if given the ion, and write the composition with the correct

notation.

Coalent bondin$

!he ionic bonding model works very well for metals and nonmetals, but for compounds made

eclusively from nonmetals, which dominate chemistry in terms of numbers, it fails completely.

!his is because nonmetals form negative ions and never positive ions. (t would also be

impossible to describe the bond between the atoms in the diatomic elements like F$, O$and +$

using the ionic model.
http://www.cod.edu/people/faculty/jarman/richenda/085_materials/CHEMICAL%20BONDING%20AND%20COMPOUND%20FORMATION.htm#_ftn3http://www.cod.edu/people/faculty/jarman/richenda/085_materials/CHEMICAL%20BONDING%20AND%20COMPOUND%20FORMATION.htm#_ftn3


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(n these elements and compounds, covalent bonding operates.

A covalent 5/5 bond is the net result of attractive and repulsive electrostatic forces. !he

nucleus/electron attractions 0blue arrows1 are greater than the nucleus/nucleus and electron/

electron repulsions 0red arrows1, resulting in a net attractive force that holds the atoms together

to form an 5$molecule.

!he sharing of electrons effectively increases the electron count around the atom. Alone, each

fluorine atom has seven electrons in the outer shell. haring two electrons in a single covalent

bond means that each atom now appears to have eight / it has satisfied its octet demand.

!he same principle applies to describing bonds between unlike atoms, such as hydrogen and

oygen in water.


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+ote that the O atom has achieved its octet by sharing one electron from each of two 5 atoms to

supplement the si valence electrons it already has.

6ultiple bonds

For some molecules, the sharing of two electrons is not sufficient to satisfy the octets of the

atoms. #onsider the series F$, O$and +$. !he elements are in groups A respectively.

!he atoms have electrons in the valence shell respectively. (t seems pretty obvious

that, if the sharing of two electrons in F$satisfied the octet, then the sharing of two electrons will

not do so in O$or +$. 5owever, more electrons can be shared, leading to multiple covalent

bonds.

)&has dou+le +ond

N&has triple +ond 9 one of the strongest in chemistry

N&is very sta+le and unreactive 9 also the ma>or product fromexplosives

+aming and writing formulas of covalently bonded compounds between nonmetals is discussed

in the document 3!ype ' #ompounds.4


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Ternar% compounds

o far we have discussed compounds that involve only two elements bonded by either ionic or

covalent bonds. !here is a class of compounds, many of them very familiar, which contain more

than two elements and also both ionic andcovalent bonding. !he compound is an ionic

compound which contains either or perhaps both ions in the form of a polyatomic ion held

together by covalent bonds.

?ost polyatomic ions are negatively charged* only the hydronium ion and the ammonium ion are

positively charged. !he rules for balancing the charges in compounds containing polyatomic ions

are the same as for binary ionic compounds. !he composition of the polyatomic ion does not

change at all.

%"&Available in the content section of the Anlon course

%$&Available in the content section of the Anlon course
http://www.cod.edu/people/faculty/jarman/richenda/085_materials/CHEMICAL%20BONDING%20AND%20COMPOUND%20FORMATION.htm#_ftnref1http://www.cod.edu/people/faculty/jarman/richenda/085_materials/CHEMICAL%20BONDING%20AND%20COMPOUND%20FORMATION.htm#_ftnref2http://www.cod.edu/people/faculty/jarman/richenda/085_materials/CHEMICAL%20BONDING%20AND%20COMPOUND%20FORMATION.htm#_ftnref1http://www.cod.edu/people/faculty/jarman/richenda/085_materials/CHEMICAL%20BONDING%20AND%20COMPOUND%20FORMATION.htm#_ftnref2


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%'&!here are some eceptions to this for the A group elements, and the transition metal ions cannot be predicted.
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Simple Procedure for Writing Lewis Structures

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