Atoms and Periodici

7/24/2019 Atoms and Periodici

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Notes: Atoms and Periodicity

Atoms:The atomsis the base or building block for all matter. The atom is the smallest particle whichstill retains all the physical and chemical properties of an element. So, if you hold a pure gold

nugget, the smallest piece of this element that would still be considered gold would be oneatom.The atom is composed ofto3 fundamental particles:,the proton, neutron and electron.

The following table describes these particles:

Particle harge !ocation A"#

p $ nucleus %

n n&a nucleus %

e ' orbit (

A"# ' Atomic "ass #nit ) %&%* the mass of a carbon'%* atom

The general concept of an atom has been around for thousands of years. Around ++( ,!eucippus of -reece originated the concept of the atom. emocritus /!eucippus0s student1,

Aristotleand , 2picurus added to this concept in the following centuries. The following pointsare key to their theories:

= correct

= incorrect

Greek Atomic Theory:%. All matter is composed of atoms, which are bits of matter too small to be seen.

*. Atoms cannot be further split into smaller portions.

3. There is a oid, which is empty space between atoms.

+. Atoms are completely solid.

4. Atoms are homogeneous, with no internal structure.

5. Atoms are different in their si6es.

7. Atoms are different in their shapes.

8. Atoms are different in their weights.

This is ama6ing,in that we are talking about men whothatlied oer *+(( years ago. At thetime they lacked the ability to properly clean their water, and frankly they did not know what theyneeded to clean in the water, and here they are correctly theori6ing on atomic structure. Themicroscope will not be inented until %49( oer a millennia awayThe ne;t solid adancement in atomic theory comes from a Pennsylania

a. si6e

b. mass

c. properties

3. Atoms of different elements are different in>

a. si6e


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b. mass

c. properties

+. Atoms cannot be subdiided, created, or destroyed.

4. ?n chemical reactions, atoms are combined, separated, or rearranged.

5. Atoms of different elements combine in simple whole number ratios to form chemical

compounds. And sometimes will create more than one compound with differing ratios.

The last point definesathe law of Definite Proportions. This law states that a moleculealways has the same ratio of atoms. @or e;ample water is A!ABS,C*D, onlyeerytwohydrogens and one o;ygen. Another e;ample, carbon dio;ide, is always D*, neer *D or*D*>carbon dio;ide will only eer be D*.

"any of these are rewritingofthe -reek theory, the new concepts are found in the final twopoints. The concept that atoms only combine in simple whole number ratiosandthethatchemical reactions are simply rearrangements of atoms. These concepts were hard for thescientific community of the %8((0s to accept. At the time Alchemy, was still holding firm, thesearch for the philosopher0s stone was ongoing. The stone was the substance that would allow

elements to be conerted to other elements through chemical means, as in the turning of lead togold.

At the time it was known that both lead and gold were pure substance, which could not bebroken down into smaller parts. alton0s theory basically told the alchemist you will neer beable to turn lead into gold. hemical reactions will only rearrange the atoms that the lead atomsare combined with, it will neer make gold.

The -reek and alton theories gae rise to Euestions of the atom0s structure. The fie mostimportant scientists inoled in the discoery of the atomic structure are>== Thomson, 2rnestFutherford, Niels ohr, erner Ceisenberg and =ames hadwick.

Thomsons theory iswascalled the Plum Pudding "odel, after a certain ritish holiday dessertforwhich ? am ery glad has neer caught on in the #SA. ?n this model the atom is a roundobGect composed of a positie mass embedded with small negatiely charged particles.Thomson named his small negatiely charged particles corpuscles. The corpuscles, thankfully,were later named electrons.

Ce discoered and proed the e;istence of electrons with the use of the cathode ray tube, theforerunner of the tube use in teleisions.


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Ernest Rutherfordmodified this structure. Cis gold foil e;periment is the key to the center ofthe atom. ?n his e;periment Futherford used the new discoery of radioactiity, a radioactieelement is aimed at a piece of gold foil. The element shoot alpha particles at a piece of gold foil.The foil wawas surround by a wall coated with a phosphorescent material. hen the alpha

particle impacted the walls a spark of light was emitted. hat Futherford0s group of scientistsfound was that most of the alpha particles passedtright through the foil. This is contrary toThomson0s model as the alpha particles are positiely charged and would surely be deflected bya solid positie mass. The ery interesting point was that the particles that did not pass throughwere deflected or scattered. Some eered only slightly off their path, fewer were scattered to alarger degree and few yet were actually deflected back the direction in which they came.Futherford therefore concluded that the atom has a ery small, densely packed, positielycharged center. Another scientist Frederick Soddyproed that the positie center is actuallycomposed of protons. Particles with and eEual yet opposite charge to that of the electron, but%839 timesmore massie.

Though theetwo charged particles had been found by %9(*, it took another 33 years for thefinal particle to be discoered. The neutron, is as its name implies, neutrally charged, in otherwords, it is not charged. This lack of a charge preented it from interacting with the manydetection deices of the time. ?t would hae been many more years before its discoery ifscientists, =ames hadwick in particular, had not been looking for the neutron. The push to findthis third particle was due to the ariations in the masses of elements from different areas of the

world. ?t seemed that elements from different regions chemically behaed the same but theatoms in the elements had a different mass. All forms of chemical analysis came up empty. Thedifference was the neutron, the uncharged particle of mass eEual to that of the proton.alton0s second assumption in his atomic theory is that all atoms of the same element areidentical in si6e, mass, and other properties. hile all atoms of the same element dohae thesame chemical properties regardless of its number of neutrons, the si6e and mass portion of thisassumption are incorrect. All atoms of the same element hae the same number of protons, butthe number of neutrons may ary.


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Atoms with the same number of protons but different numbers of neutrons are isotopes of eachother. An interesting note is that most isotopes of a gienelement are radioactie, only one ortwo are stable,non'radioactie.The final two scientistsinoled in the deelopment of the atomic structure are Niels ohr anderner Ceisenberg. !ike Futherford, these two did not discoer one of the particles but insteadthey described where these particles are to be found. oth ohr and Ceisenberg describedwhere the electron resides in the atom. ohr deeloped his model in %9%3, his model is the one

that most of us enision when thinkingabout the atom>,it follows a planetary model.Futherford0s nucleus acts like the sun to which the tiny planetary electrons orbit. The electronsare place around the nucleus in symmetrically larger orbits or shells as they were called. 2achshell holdsinga specific number of electrons.ohr0s model is a good one, and is ery intuitie>,the problem was that it did not describe all thedata that was being rapidly collected. ohr0s colleague Ceisenberg deeloped our currentatomic model based on the newly found science


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he fostered it, championing the idea to the world on behalf of his fellow scientist, this is howCeisenberg0s and many other brilliant scientists0ideas found widespread acceptance.

As stated more than *((( years ago, atoms are ery small. So,small we still do not hae thetechnology to photograph one. Si6e'wise a, an atomis si6eis in the %('%(meter range. Actually,in %9*4, erner Ceisenberg, the author of the currently accepted model for the atom stated thata photography of atomic si6ed particles is impossible. ?t is termed Ceisenberg0s uncertaintyprincipal. The premise is that the atom is so small, that the light used to photograph the atom isstrong enough to moe the atom, so now the atom is no longer where it was andyouis nolonger in the picture.

All atoms are neutrally charged, m. "eaning they are composed of eEual numbers of protonsand electrons and,with the e;ception of hydrogen,a certain number of neutrons. Since theneutrons hae no charge, the atoms neutrality is unaffected by number of neutrons.!ooking at the aboe table you will see that the electron has no mass, ( A"#. This is notcompletely true, but its mass, as stated before, is around *(((timesless than that of a protonor neutron. So, when discussing an atom0s mass a count of the protons and neutrons is all thatis needed. An atom with + protonsand 4 neutrons has an atomic mass of 9 A"#.The atomic number of an atom is simplyeits number of protons. @or e;ample all carbon atomshae 5 protons. ?f you add another proton you no longer hae carbon you now hae nitrogen. ?fyou were gien the following table but it only contained the black numbers and symbols youshould be able to fill in the bo;es with the red numbers and symbols.

symbol atomic H neutrons electrons atomic massNa %% %* %% *3


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P %4 *( %4 34# 9* %+5 9* *38Ti ** *4 ** +7

Diatomics and Allotropes:"ost of the elements on the periodic table are found as indiidual atoms ,in their elemental

state. ut a few are found linked to themseles. A diatomic is an element that is found pairedwith itself. There are seen diatomics found in nature on the surface of the 2arth. C*, N*, D*,@*, l*, r*and ?*. ith the e;ception of hydrogen, they are all found together and they are allnon'metals. Bes, o;ygen will form a three atom triatomic, but only in the ery upper atmosphereat ery low pressures.The name for these elements found in different combination with themseles is allotrope. So,you would say that D*and D3are allotropes of each other. Sulfur forms an interesting S8allotrope. arbon has three noteworthy allotropes, graphite /found in your pencils1, diamonds/hopefully found on your finger1 and the uckyball /shaped like 2pcot enter or a soccer ball1.

graphite diamond uckyball


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Periodic Tale and Periodicity:This table holds so much information. ?t is easily the most important tool of a chemist. Some sitand stare at it like art, similar to those 3 drawings when after staring for a while an image popsout at you, an idea may emerge from the table. This is not a random collage of strange names,there is meaning to its arrangement.Periodicity, as defined by ebster0sis:Ithe Euality, state, or fact of being regularly recurrent orhaing periods.J As this concept applies to the periodic table, at regular interals you will find

elements with similar chemical properties if the elements are placed in order of ascendingatomic number. So, periodically the elements in the periodic table hae similar physical andchemical properties.?n %895, the Fussian chemist mitri "endelee, usually regarded as father of the periodic table,pinned cards of all the elements on a boardand,tried to arrangethemin a pattern. !egendclaims hesat back in his chair and staredat the board of elements. Ce eentually drifted off tosleep and when he awoke, comprehendedthe importance of the periodicity and finali6ed thefirst basic periodic table.The most ama6ing facet of his table wasereits holes. Ce recogni6ed that een though theelements are arranged in order of increasing mass /later by atomic number1 for all of theelements in a certain column to hae the same properties he would need to skip a column in the

table to better place that element in it own family. Ce actually predicted that eentuallyscientists would find new elements to fit in those holes. And he was right

2arlier ? stated that "endelee is usually regarded as the father of the periodic table. ? sayusually because =ulius "eyer, a -erman chemist, actually published a similar table at the sametime. So, if you find yourself in the company of -erman chemists they might remind you that"endelee was not the firstand that , the great chemist "eyer, had at the same time, came tothe same conclusions.

The columns, ertical, are called -roups or @amilies, and react similarly from top to bottom.The rows, hori6ontal, are called periods.,2elements ne;t to each other may react similarly, but

from side to side they are K2FB different. As you moe across a period, the number of protonsin each element is increased by one.

hat does react similarly meanL Take Na and M. oth react with water, both are in a %:% ratiowith group 7 elements, they een taste similar. They each hae one outer electron. Thenumber of outer electrons causesthe elements to react similar.

2lements with one outer electron react the same, elements with 7 outer electrons react thesame. This is the origin of the periodicity "endelee really had no idea why, he had noknowledge of electrons. hen they were discoered he did not beliee in their e;istence and sohe did not think they were responsible for his periodicity. ut he was incorrect>,the periodicity is

due to the elements haing the same number of outer electrons, called alence electrons.

e now must discuss the arrangement of electrons about the atom in more detail, on a moreEuantum mechanical leel. on0t get oerwhelmed by all the terminology that follows, it allcomes back to the structure of the periodic table.


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mitri "endelee0s first hand written and typed drafts of the periodic table.

mitri "endelee


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Ener!y "e#els:2lectrons are found outside the nucleus of the atom. Their locations are highly organi6ed. =.=.Thomson theori6ed the electron was IstuckJ to the surface of the atom, Niels ohr0s postulateda solar system like model and finally erner Ceisenberg used>Euantum mechanics, calculusand wae functions to describe the electron0s whereabouts.

Fegrettably, ery few people can follow the math thatwhiche;plains Ceisenberg0s theory. ut

the results can be followed. Some of ohr0s model is still useful for isuali6ing the electron0slocations.

The electron0s location will be described in terms of a Principal 2nergy !eel, a Subleel, anorbital and a Spin characteristic. 2ach spinning electron is found in an orbital. Drbitals makeupa subleel and the subleels complete the principal energy leel.

There are seen principal energy leels. Dne for each row on the periodic table. 2achsuccessie leel is able to hold another subleel. The %stprimary energy leel contains only %subleel, the second primary energy leel contains * subleels.,Tthis trend continues to the 7thprimary energy leel, which, this leelcontains 7 subleels.

The subleels are named by a single letter. The first subleel is the s, followed by p, d, f, g, h i. The first four subleels are the most important. There are seen subleels. 2ach successieleel is able to hold two more orbitals.

The %stsubleel, s, can hold % orbital. the *ndsubleel, p, can hold 3 orbitals. This trendcontinued in the following table:

2nergy !eel Subleels per leel

% s

* s p

3 s p d

+ s p d f 4 s p d f g

5 s p d f g h

7 s p d f g h i

2ach subleel is able to hold a specific number of orbitals. And each orbital can hold only twoelectrons. The total number of electrons that a subleel can hold is listed in the below table.

Subleel Drbitals per Subleel 2lectrons per Subleel

s % *

p 3 5

d 4 %(

f 7 %+

Bou may be asking yourself why the g, h, and ? subleels are not listed here. That is a erygood Euestion and there is a ery good answer. No element e;ists which has so manyelectrons that the g, h or i subleels will eer be filled.


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The periodic table will tell you how many electrons will fit into each subleel. The shape of thetable is based on the arrangement of the electrons. The below table is color codedintoblocks. The greenish area is the s'block, the red area is the p'block, the yellow area is thed'block and the blue area is the f'block. This will tell you how many electrons will fit into asubleel.

The s'block is * column wide, the s'block will hold * electrons as it contains % orbital.

The p'block is 5 column wide, the p'block will hold 5 electrons as it contains 3 orbital.The d'block is %( column wide, the d'block will hold %( electrons as it contains 4 orbital.The f 'block is %+ column wide, the f 'block will hold %+ electrons as it contains 7 orbital.

Femember, each orbital can hold * electrons.

The table may be show in the following manner. Bou normally see it in the aboe mannerbecause itasis more condensed and will fit on a page more easily.


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$rital Shapes:This is what the wae function orbitals look like in calculus.


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Electron %onfi!urations:The notation to identify the location of each electron within an atom is the electron sconfiguration. 2ach electron has a specific spot or orbit where it will be found. The orbits ororbitals are shown in the aboe diagrams.The format is to gie the number of the energy leel, followed by the subleel letter and then thenumber of electrons in that subleel written as a superscripted number ne;t to the subleelletter. Cere are two e;amples:

hydrogen

carbon

%s% %s**s**p*

The electron configuration accounts for all electrons in the atom. The hydrogen atom has oneelectronand , that electron is found in the first energy leel >,it is found in the s subleel and thesubscript shows the one electron in that subleel.

The carbon atom contains 5 electrons. The first two electrons are in the first energy leel and in

the s subleel. The first energy leel can only hold one subleel and the s subleel can onlyhold one orbital so it can only house the * electrons. So we must add ourtne;t two electrons tothe second energy leel. The first two electrons are placed in the s subleel. A, again,since ssubleels can only hold one orbital, soit can only hold * electrons and we must moe on to thene;t subleel in the second energy leel. The second energy leel can hold two subleel, s andp.The last two electrons can fit in the p subleel as the p subleel can hold 3 orbitals.

The electron configurations of the noble gasses act as a stepping point to the ne;t energy leel.These configurations proide a break point when writing long configurations. Since eeryelement past a noble gas will hae the same configuration up to that noble gas ,it is used as an

abbreiation. See the following e;amples.

@ull onfiguration S: %s**s**p53s*3p+ Na: %s**s**p53s% e: %s**s*

Noble -as onfiguration S: ONe 3s*3p+ Na: ONe 3s% e: OCe*s*

$rder of Fillin! Sule#els:#nfortunately, electrons do not fill all of the subleels contained in a gien energy leel beforethey begin to fill the subleels in the ne;t, higher energy leel.The following diagram lays out the order in which the subleels are filled.


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Ener!y "e#el Dia!rams:These diagrams depict which energy leels and subleels the electrons are found in. ?n thesediagrams the lines indicate orbitals and the arrows indicate electrons. The energy leeldiagrams for C and atoms are as follows:

Two things may strike you as you look at the carbon atom 0s energy leel diagram. @irst, why arethe arrows alternating in directionL The Pauli 2;clusion Principal states that electrons hae spin

and electrons in the same orbital must hae opposite spin. The reason for this is that electronsare negatiely charged, so they repel each other. ut, when a charged particle spins itproduces a magnetic field. ?n the picture below the electrons are spinning in opposite directionsproducing opposite magnetic fields and the norths and souths are attracted to each other. So,een though the negatie charges are forcing the electrons apart, at least their magnetic fieldsare pulling them together.

The second point of interest in carbon0s energy leel diagram is the Euestion as to why the toptwo electrons not in the same orbitalL Cund0s Fule states that electrons fill empty orbitals in thesame subleel before combining electrons in the same orbital> because, asthey are bothnegatiely charged,they want to stay as far away from each other as possible.


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Groups of the Periodic Tale:

?#PA-roupnumbers

#S-roupnumbers

Actiity Namesharges@ormed

Kalence2lectrononfiguration

% %A ery reactie alkali metals $% s%

* *A reactie alkali earths $* s*

%3 3A semi'reactie ' $3 s*p%

%+ +A mildly reactie ' $+ or ' + s*p*

%4 4A semi reactie ' '3 s*p3

%5 5A reactie ' '* s*p+

%7 7A ery reactie halogens '% s*p4

%8 8A non'reactie noble gasses none s*p5

The d ' block is called the transition metals. These elements are strange in that when they reactthey use different numbers of their electrons depending on the other reactant/s1 andenironmental conditions.

The f ' block is called the lanthanide and actinide series. "ost are ery rare and so they arealso named rare earths or rare earth metals or inner transition metals. The elements in theactinide series, past uranium are all man made, these elements are called transuranium.

lasses of 2lements:!ooking at the below diagram you will see a red stair&step line. This is the periodic table0sdiiding line. Dn the left side of the line you will find the metal /with the acceptation ofhydrogen1. Dn the right side of the line you will find the non'metals. Those elements touchingthis stair&step lineare considered metalloids. "etalloids hae properties of both metals andnon'metals.

The properties of these three classes of elements, both chemical and physical, ary greatly.


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"etals physical properties include: being a solid at STP, standard temperature and pressure,/e;cept for mercury1and haing , high electrical and thermal conductiity, lusterrous, malleabilityand ductility. Substances,which e;hibit luster characteristics,reflect light well. "alleablesubstances,can be flattened into sheets. uctilityerefers to a substance0s ability to be pulledinto a wire. Another interesting point about metals is their ability to form a homogeneousmi;ture, an alloy, with other metals. The properties of the alloy areisdifferent than thoseatof thecomponentsmetals. An alloy is normally stronger, more heat resistant and more resistant to

corrosion. Steel is the most common alloy. hen undergoing a spontaneous chemical reactionmetals lose electrons to non'metals forming ionic compounds.

The physical properties of non'metals are less uniform than those of metals. At STP, many non'metals are gasses /o;ygen, neon...1, a few are solids /sulfur, iodine...1 and one is a liEuid/bromine1.

Non'metals are poor thermal and electrical conductors. The solid non'metals are powders orare brittle, they cannot be formed into any structurally sound shape.hen chemically reacting with metals, non'metals tend to gain electrons to form anions, butnon'metals share electrons when forming compounds with other non'metals,to create coalent

compounds.

Relati#e Atomic Si'e:An aAtom is appro;imately %('%(m in diameter. ut each element0s atoms are a slightly differentsi6e. #sing the periodic table as a guide, as you moe down a group /column1, the atombecomes larger. ut as you moe across a period /row1, the atoms become smaller.

(oni'ation Ener!y:hen an atom0s charges are not balanced, it has more electrons than protons or less electronsthan protons> therefore,the atomsbecomes is a charged species and is now an ion. Theamount of energy needed to remoe andelectron from an atom is termed ioni6ation energy.

The periodic table is used as a guide to relatie ioni6ation energies of atoms. As you moedown a group less energy is reEuired to remoe an electron. onersely, as you moe acrossthe periods more energy is needed to remoe an electron. Celium is the most difficult atomfrom which to remoe an electronfrom. @rancium releases itsalence electron most easily.


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Electrone!ati#ity:hemical reactions occur as atoms attempt to fill energy leels. Some atoms fill energy leelsby adding electrons while others gie up their electrons. An atom0s electronegatiity is ameasure of that atom0s affinity for electrons. Again, the periodic table can be used as a guide.The relatie electronegatiity of atoms decreases as you moe down a group ,theelectronegatiity of the atoms decreases. Dn the other hand, as you trael across a period theelectronegatiity increases. These rules e;clude the noble gasses as they already hae filledenergy leels and do not react chemically unless forced by e;treme enironmental conditions.

The most electronegatie element is fluorine and the least is francium. @luorine can be thoughtof as the bully of the periodic table. ?t has the ability to take an electron from all other types ofatoms, again with the acce;ceptation of the nNobelegasses.,?in the bully analogy ? relatenoble gassesthemto the parents of the elements, a they cannot be bullied.

Awesome eb Site:http:&&www.colorado.edu&physics&*(((&periodicQtable


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"e)is Dot Structures:A !ewis ot iagram is a simple way to show how many electrons will be inoled in a chemicalreaction. These electrons are named the atom0s alence electrons as they are in the outer leelof the atom and are most accessible for a reaction to occur. !ewis recogni6ed that atomsgained or lost electrons in an effort to complete or fill this alence leel. The electrons inside ofthis alence leel are not aailable for reacting.The electrons in the alence leel are those added after the last noble gas configuration. !ewis

used dots around the atom0s symbols to show that atom0s number of alence electrons.2;ample %:Sodium has % alence electron, the electron configurations is *s++s++p,-s*

The blueportion of the electron configuration is the noble gas configuration of neon. The oneelectron added after neon, shown in red, is found in the 3s%sub'leel

NaR2;ample *:@luorine has 7 alence electrons, the electron configuration is *s++s++p.

?f we look at the periodic table the group tells us the number of alence electrons. ut, this onlyapplies to the s and p blocks. ?t does notapply tothe transition metals or d' block.

All group %A elements hae % alence electron, therefore % dotAll group *A elements hae * alence electron, therefore * dotAll group 3A elements hae 3 alence electron, therefore 3 dotAll group +A elements hae + alence electron, therefore + dotAll group 4A elements hae 4 alence electron, therefore 4 dotAll group 5A elements hae 5 alence electron, therefore 5 dotAll group 7A elements hae 7 alence electron, therefore 7 dotAll group 8A elements hae 8 alence electron, therefore 8 dot

The term octet has come out of this line of thought. There are 8 groupsin the aboe list. henatoms react with other atoms theyatomsappear to be collecting or losing electrons to arrie at 8total alence electrons or an octet.

!ook at the aboe two e;amples.

?f sodium is to lose % electron, it will hae 8 alence electrons, found in the *s **p5orbitals.?f fluorine gains % alence electron, it will hae 8 alence electrons found in the *s **p5orbitals.

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