Unit 1 Mod 1 Atomic Structure and Periodic Table (1)

7/21/2019 Unit 1 Mod 1 Atomic Structure and Periodic Table (1)

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ATOMIC STRUCTURE AND THE PERIODIC TABLE

Theoretical change with respect to Dalton’s atomic theory

1. In 1803, atomic theory was revived by John Dalton a matter is made !p o" tiny particles called atoms which cannot be created,

destroyed or split

b all atoms o" one element are identical#$ same mass and same chemical

properties

c a chemical reaction consists o" rearranging atoms "rom one combination to

another.

d %hen elements combine to "orm compo!nds, small whole n!mbers o" atoms

"orm molec!les.

&owever this was proved to be not entirely correct. 'toms have been spl

it as

well as created i.e. n!clear reactions. 'lso there are isotopes, meaning that not

all atoms o" an element are identical.

There"ore theory was "orced to (&')*+ in regards to these observations

contradicting to the theory

p!t "orward by Dalton.

The distrib!tion o" charge and mass in an atom

Particle Location Mass Charge

Electron rbitals 1-183 !nit $1 !nit

Proton )!cle!s 1 !nit /1 !nit

Neutron )!cle!s 1 !nit 0

'tomic tr!ct!re page 1 o" 0

' !nit is one atomic mass !nit 2 1. 4 10$



'tomic tr!ct!re page o" 0



Terminology

Term

Definition

Atomic/proton number )!mber o" protons in a n!cle!s o" an atom Nucleon/mass number !m o" the n!mber o" protons and ne!trons in the

n!cle!s o" an atom

Nuclide 'ny atomic species o" which the proton n!mber and

n!cleon n!mber are speci"ied e.g. 1( and 6

7 are

n!clides

Isotopes )!clides o" the same element or atoms o" the same

element with di""erent mass n!mbers

) isotopes have the same chemical properties b!t

di""erent physical properties Relatie atomic mass 9ass o" an atom based on a scale s!ch that the ($1

isotope has a mass o" 1.00 !nits

relative atomic mass

2 mass o" 1 atom o" an element 4 1

mass o" 1 atom o" carbon$1




:henomenon o" radioactivity

;adiation is the spontaneo!s decay o" !nstable atoms with the emission o" either

alpha, beta or gamma radiation.

Alpha decay is a type o" radioactive decay in which an atomic n!cle!s emits an

alpha particle <two protons and two ne!trons bo!nd together into a particle

identical to a heli!m n!cle!s and trans"orms <or =decays= into an atom with a

mass n!mber 7 less and atomic n!mber less.

>or e4ample#

altho!gh this is typically written as#

Beta decay is a type o" radioactive decay in which a "ast moving ele

ctrons is

emitted. The new atom has no change in mass n!mber b!t an atomic n!mber

increases by 1.

Gamma rays or gammaray <denoted as ? are "orms o" electromagneticradiation <+9; or light emissions o" a speci"ic "re@!ency prod!ced "rom s!b$

atomic particle interaction, s!ch as electron$positron annihilation and

radioactive decay. There is no change in atomic or mass n!mber o" the atom.

Ba!d "# sta$%l%ty &!'p rat%"(


9ost elements have isotopes. >or stable

isotopes, an interesting plot arises when

the n!mber o" ne!trons is plotted vers!s

the n!mber o" protons.

eca!se the plot shows only the stable

isotopes, this graph is o"ten called the )!clear elt o" tability.

The plot indicates that lighter n!clides

<isotopes are most stable when the

ne!tron-proton ratio is 1-1. This is the

case with any n!cle!s that has !p to 0

protons.

's the atomic n!mber increases beyond0, a di""erent trend becomes apparent. In

this range, it appears that a stable n!cle!s

is able to accommodate more

ne!trons. table isotopes have a higher

ne!tron to proton ratio, rising to 1.A-1 "or

elements having atomic n!mbers

between 0 and 83.

http://en.wikipedia.org/wiki/Radioactivity


http://en.wikipedia.org/wiki/Atomic_nucleus



http://en.wikipedia.org/wiki/Alpha_particle

http://en.wikipedia.org/wiki/Atomic_weight

http://en.wikipedia.org/wiki/Atomic_number


http://en.wikipedia.org/wiki/Radioactive

http://en.wikipedia.org/wiki/Gamma

http://en.wikipedia.org/wiki/Electromagnetic_radiation


http://en.wikipedia.org/wiki/Photon

http://en.wikipedia.org/wiki/Atom


http://en.wikipedia.org/wiki/Electron-positron_annihilation

http://en.wikipedia.org/wiki/Radioactive_decay

http://def%28%27/Glossary/glossaryterm.aspx?word=Graph%27,%20500,%20500);

http://def%28%27/Glossary/glossaryterm.aspx?word=Ratio%27,%20500,%20500);

http://def%28%27/Glossary/glossaryterm.aspx?word=Nucleus%27,%20500,%20500);

http://def%28%27/Glossary/glossaryterm.aspx?word=Atomic%20Number%27,%20500,%20500);


http://def%28%27/Glossary/glossaryterm.aspx?word=Neutron%27,%20500,%20500);

http://def%28%27/Glossary/glossaryterm.aspx?word=Proton%27,%20500,%20500);


http://en.wikipedia.org/wiki/Alpha_particle

http://en.wikipedia.org/wiki/Atomic_weight


http://en.wikipedia.org/wiki/Radioactive

http://en.wikipedia.org/wiki/Gamma



http://en.wikipedia.org/wiki/Photon



http://en.wikipedia.org/wiki/Electron-positron_annihilation

http://en.wikipedia.org/wiki/Radioactive_decay

http://def%28%27/Glossary/glossaryterm.aspx?word=Graph%27,%20500,%20500);

http://def%28%27/Glossary/glossaryterm.aspx?word=Ratio%27,%20500,%20500);


http://def%28%27/Glossary/glossaryterm.aspx?word=Atomic%20Number%27,%20500,%20500);


http://def%28%27/Glossary/glossaryterm.aspx?word=Neutron%27,%20500,%20500);

http://def%28%27/Glossary/glossaryterm.aspx?word=Proton%27,%20500,%20500);




Bses o" radioisotopes

1. radiocarbon dating . smo5e detectors

3. pacema5ers 7. medical !ses i.e. trace

rs or chemotherapy

A. irradiation in pest control

(alc!lations o" relative atomic mass "rom isotopic data

'r o" an element 2 s!m o" <ab!ndances 4 mass n!mber o" all o" the isotopes o"

an element

e.g. Circoni!m$60 A1.A Circoni!m$61 11. Circoni!m$6 1.1

Circoni!m$67 1.7 Circoni!m$6 .8

'r Circoni!m 2 <A1.A 4 60 / <11. 4 61 / <1.1 4 6 / <1.7 4 67 / <.8 4 6

2 6131.8

The average mass o" these 100 atoms wo!ld be 6131.8 - 100 2 61.3 <to 3

signi"icant "ig!res.

)*+, %s the relat%-e at"m%c mass "# .%rc"!%/m.

+vidence o" discrete energy levels !sing emission spectra

'tomic tr!ct!re page A o" 0



'n element=s em%ss%"! spectr/m is the relative intensity o" electromagnetic

radiation o" each "re@!ency it emits when it is heated <or more generally when it

is e4cited.

%hen the electrons in the element are e4cited, they E!mp to higher energy levels.'s the electrons leave the e4cited state and "all bac5 down, energy is emitted,

the wavelength o" which re"ers to the discrete lines o" the emission spectr!m. I"

discrete energy levels were )T present, no lines co!ld +F+; be "ormed in an

emission spectr!m.

e.g. emission spectr!m o" hydrogen

+mission spectr!m o" hydrogen

%hen a gaseo!s hydrogen atom i

n its gro!nd state is e4cited by an inp!t o"

energy, its electron is =promoted= "rom the lowest energy level to one o" higher

energy. The atom does not remain e4cited b!t re$emits energy aselectromagnetic radiation. This is as a res!lt o" an electron ="alling= "rom a higher

energy level to one o" lower energy. This electron transition res!lts in the release

o" a ph"t"! "rom the atom o" an amo!nt o" energy <+ 2 h ν e@!al to the

di""erence in energy o" the electronic energy levels involved in the transition.

In a sample o" gaseo!s hydrogen where there are many trillions o" atoms all o"

the possible electron transitions "rom higher to lower energy levels will ta5e

place many times. ' prism can now be !sed to separate the emitted

electromagnetic radiation into its component "re@!encies <wavelengths orenergies. These are then represented as spectral lines along an increasing

"re@!ency scale to "orm an at"m%c em%ss%"! spectr/m.




http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Light_emission

http://en.wikipedia.org/wiki/Heat

http://en.wikipedia.org/wiki/Electrons

http://en.wikipedia.org/wiki/Chemical_element



http://en.wikipedia.org/wiki/Frequency

http://en.wikipedia.org/wiki/Light_emission

http://en.wikipedia.org/wiki/Heat





Gyman series occ!rs when electrons drop "rom higher energy levels to the

gro!nd state <n 2 1, in this series, the m"st amo!nt o" energy is released and

th!s the smallest wavelength and highest "re@!ency. In the almer series, all

electrons drop to the n2 level, here energies released are not as high as in the

Gyman series. ;emember energy is directly proportional to "re@!ency b!tindirectly proportional

)ote that within each series, the spectral lines get closer together with increasing

"re@!ency. This s!ggests that the electronic energy levels get closer the more

distant they become "rom the n!cle!s o" the atom.

)o two elements have the same atomic emission spectr!mH the atomic emission

spectr!m o" an element is li5e a #%!gerpr%!t.


Gyman series occ!rs when

electrons drop "rom higher

energy levels to thegro!nd state <n 2 1, in

this series, the m"st

amo!nt o" energy is

released and th!s the

smallest wavelength and

highest "re@!ency. In the

almer series, allelectrons drop to the n2

level, here energies

released are not as high as



At"m%c "r$%tals

!uantum number Definition

"irst principal #uantum number $n% This corresponds to the shell n!mber

e.g. the 1st shell has n21, nd shell has

n2

1. Or$%tal vol!me o" space in which there is a 6A chance o" "inding an

electron

. S/$shell a gro!p o" orbitals with the same energy i.e. they are

degenerateK

e.g. 3p s!bshell which has 3 orbitals o" the same energy

3. Shell a gro!p o" orbitals and-or s!bshells with the same principal @!ant!mn!mber. n 21 shell is called the L shell, n2, the G shell, n23 the 9 shell

etc.

Pr%!c%pal 0/a!t/m !/m$er Types "# "r$%tals's/$shells prese!t

%! the shell

n21 1s orbital

n2 s orbital and p s!bshell <which

contain T&;++ p orbitals

n23 3s orbital, 3p s!bshell <T&;++ p

orbitals and 3d s!bshell <>IF+ d

orbitals

The relat%-e e!erg%es "# s1 p a!d d "r$%tals /p t" pr%!c%pal 0/a!t/m

!/m$er 2

)ote# The 7s orbital is G%+; than the 3d orbital. There"ore electrons will

enter the 7s orbital "irst be"ore the 3d




Shapes "# at"m%c "r$%tals &s "r$%tal a!d p "r$%tal respect%-ely(

Order "# #%ll%!g electr"!s %! "r$%tals 3 s/$shells &electr"!%c

c"!#%g/rat%"!(

1s s p 3s 3p 7s 3d

+ach orbital can hold only T4O electrons. +lectr

ons entering s!b$shellscontaining or more orbitals enter and occ!py the orbitals SINGL5

be"ore pairing. 'n orbital o" lower energy m!st be "illed 6IRST be"oreelectrons enter an orbital o" a higher energy level.

Eleme!t *s 7s 7p8 7py 7p8 ,s ,p8 ,py ,p. 2s ,d

*H 1

7He

,L% 1

2Be

9B 1

:C 1 1

;N 1 1 1

<O 1 1

)6 1

*=Ne **Na 1

*)> 1

7=Ca


;emember "or each p s!b$

shell, there are 3 p orbitals in

4, y and C a4is called p4, py and pC. They are

perpendic!lar to each other.

They are o" the same energy

level and are called

dege!erateK.



Eleme!t *s 7s 7p8 7py 7p. ,s ,p8 ,py ,p. 2s ,d

7*Sc 1

77T%

7,? 372Cr@ 1 A

79M! A

7:6e A

7;C"

7<N% 8

7)C/@ 1 10

,=! 10

@ I!d%cates that the electr"!%c c"!#%g/rat%"! %s !"t hat %s e8pected.

For Cr what would have been expected would be 3d

4 4s2 , however, half filled

and totally filled shells/orbitals are very stable and thus more preferred than

any other configuration. herefore the electrons half fill the 3d subshell

with ! electrons and half fill the 4s orbital with " electron.

For Cu, what would be expected was 3d

# 4s2 , again the combination of atotally filled subshell and a half filled orbital is more stable than $ust a filled

orbital and a partly filled subshell. herefore the electrons adopt the more

stable configuration.

E-%de!ce "# d%screte e!ergy le-els /s%!g em%ss%"! spectra

ased on in"ormation given above, it is shown that energy occ!py di""erent

orbitals or even$s!bshells and in essence occ!py discrete energy levels.%hen elements !ndergo emission spectroscopy and prod!ce an emission

spectr!m, a series o" lines are shown li5e the emission spectr!m o" hydrogen

shown below.




B/t h" are these l%!es e8pla%!ed a!d h" d" they sh" e-%de!ce "#

d%screte e!ergy le-els

%hen the electrons in the element absorb energy, they move to higher energylevels and are no longer in the gr"/!dK state <lowest energy state, they are

now in an e8c%tedK state <state o" higher energy. 's the electrons release the

energy absorbed and leave the e4cited state to ret!rn to the gro!nd state, the

e4cess energy is emitted, the wavelength o" which re"ers to the discrete lines o"

the emission spectr!m. I" discrete energy levels were NOT present, no lines

co!ld E?ER be "ormed in an emission spectr!m.

Em%ss%"! spectr/m "# hydr"ge!

%hen a gaseo!s hydrogen atom in its gro!nd state is e4cited by an inp!t o"energy, its electron is =promoted= "rom the lowest energy level to one o" h

igher

energy &s%m%lar #r"m m"-%!g #r"m a l"er r/!g %! a ladder t" a h%gher

r/!g(+ The atom does not remain e4cited b!t re$emits the e4cess energy as

electromagnetic radiation. This is as a res!lt o" an electron ="alling= "rom a higher

energy level to one o" lower energy. This electron transition res!lts in the release

o" a ph"t"! "rom the atom o" an amo!nt o" energy <+ 2 hv e@!al to the

di""erence in energy o" the electronic energy levels involved in the transition.

N"te E e!ergy1 h Pla!cFs c"!sta!t a!d - #re0/e!cy "# a-ele!gth "#

rad%at%"! em%tted

In a sample o" gaseo!s hydrogen where there are many trillions o" atoms all o"

the possible electron transitions "rom higher to lower energy levels will ta5e

place many times. ' prism can now be !sed to separate the emitted

electromagnetic radiation into its component "re@!encies <wavelengths or

energies. These are then represented as spectral lines along an increasing

"re@!ency scale to "orm an at"m%c em%ss%"! spectr/m.








In each spectra a gro!p o" lines are see together which is classi"ied as a ser%es.

There are 3 series which are o" signi"icance.

The Lyma! ser%es occ!rs when electrons drop "rom higher energy levels to the

gro!nd state <n 2 1, in this series, the m"st amo!nt o" energy is released andth!s the smallest wavelength and highest "re@!ency. This is why Gyman series

corresponds to the !ltra$violet region <high energy

The Balmer ser%es occ!rs when electrons drop "rom higher energy levels to the

n 2 level, here energies released are not as high as in the Gyman series. This

corresponds to the visible region o" electromagnetic <+9 spectr!m.

The Pasche! ser%es occ!rs when electrons drop "rom higher energy levels to then 2 3 level. This corresponds to the in"ra$red region o" electromagnetic <+9

spectr!m.

)o two elements have the same atomic emission spectr!mH the atomic

emission spectr!m o" an element is li5e a #%!gerpr%!t.

I"!%sat%"! e!ergy

It can be @!oted more acc!rately as either 1st, nd, 3rd, 7th etc ionisationenergy. >or o!r p!rposes, we will deal with the 1st ionisation energy.

The *st %"!%sat%"! e!ergy %s the e!ergy re0/%red t" rem"-e a m"le "#

electr"!s #r"m a m"le "# gase"/s at"ms t" #"rm a m"le "# gase"/s

/!%-ale!t %"!s+ A &g( A &g( e

Trend o" 1st

ionisation energies

I"!%sat%"! e!erg%es

ge!erally %!crease g"%!g acr"ss a per%"d

;emember two "actors m!st be considered# <1 proton n!mber increases

se@!entially going across a period i.e. greater n!clear attraction "or the

o!termost electron<s and < n!mber o" electrons are also increasing.

'ltho!gh the addition o" electrons into the shell ca!ses rep!lsion and th!s

wo!ld increase the atomic radi!s, the predominant "actor is the increasede""ective n!clear chargeK <which is the resid!al attraction o" the n!cle!s

and the o!termost electron<s a"ter shielding o" the inner electrons i.e. more

energy wo!ld be needed to remove the o!termost electron<s. Th!s

ionisation energy increases "rom le"t to right o" a period




I"!%sat%"! e!erg%es decreases g"%!g d"! a gr"/p

'ltho!gh n!clear charge increases, the dominant "actor is the increasing n!mber

o" shells between the n!cle!s and the o!termost electron<s. This res!lts in

increased shielding o" the n!clear charge, there"ore less attraction o" the n!cle!sand the o!termost electron<s i.e. less energy needed to remove an o!termost

electron. Th!s ionisation energy decreases down a gro!p.

Atyp%cal $eha-%"/r see! %! per%"d , #"r Mg 3 Al AND P 3 S &per%"d ,(

In period 3, 9g has +.(. o" M)eN 3s, while 'l has +.(. o" M)eN 3s 3p41, in 'l the

o!termost electron <3p is at a h%gher energy level than the o!termost electron in

9g <3s, there"ore less energy is needed to remove it. r !sing a di""erent

e4planation, the valence electron in 'l e4periences more shielding i.e. lessn!clear attraction than one o" the valence electrons in 9g i.e. less energy needed

to remove it "rom 'l than "or 9g.

In period 3 "or : and , the e4planation needed is somewhat di""erent. >or :, the

+.(. is M)eN 3s 3p3, while "or the +.(. is M)eN 3s 3p7. In the 3p s!bshell o" :,

the hal"$"illed s!bshell represents a -ery sta$le con"ig!ration since it represents

a system o" minim!m rep!lsion as each electron occ!pies one orbital singly. '

l"t o" energy wo!ld be needed to disr!pt this con"ig!ration. %hile in , 3p

s!bshell e4periences electron$electron rep!lsion in one o" its orbital which raisesthe energy o" the system, there"ore it is G+ stable and G+ energy wo!ld be

needed to remove one o" the valence electrons.

elow is a diagram "or the 1st ionisation energy o" period 3 elements. )ote

the circles show the areas o" atypical behavio!r




E-%de!ce "# s/$shells /s%!g %"!%.at%"! data

The graph $el" sh"s the s/ccess%-e %"!%.at%"! e!erg%es #"r a! at"m "#

s"d%/m

The electronic str!ct!re "or sodi!m is 1s s p 3s1.

The energy re@!ired to

remove the "irst electron is relatively low. This corresponds to the loss o" one3s electron. To remove the second electron needs a m!ch greater energy

beca!se this electron is closer to the n!cle!s in a p orbital. There is a steady

increase in energy re@!ired as electrons are removed "rom p and then s

orbitals.

The removal o" the tenth and eleventh electrons re@!ires m!ch greater

amo!nts o" energy, beca!se these electrons are closer to the n!cle!s in the 1s

orbital.

Garge E!mps in energy shown by the circles, indicate moving "rom one

principal @!ant!m n!mber to another. The smaller, more grad!al increases

indicate going moving within s!bshells as the energies o" the electrons will

slowly decrease res!lting in more and more energy needed to remove them.




H" t" der%-e gr"/p !/m$er "# a! eleme!t #r"m s/ccess%-e %"!%.at%"!

e!erg%es

' large E!mp <!s!ally an increase o" 3 or more times the amo!nt between

two s!ccessive ionisation energies is typical o" s!ddenly brea5ing in to an

inner level. Oo! can !se this to wor5 o!t which gro!p o" the :eriodic Table

an element is in "rom its s!ccessive ionisation energies.

E8ample * 9agnesi!m <1ssp3s is shown with the "ollowing

s!ccessive ionisation energies#

&ere the big E!mp occ!rs a"ter the second ionisation energy. It means that

there are electrons which are relatively easy to remove

<the 3s electrons,

while the third one is m!ch more di""ic!lt <beca!se it comes "rom an inner

level $ closer to the n!cle!s and with less screening. 9g is there"ore ingro!p II

E8ample 7 ilicon <1ssp3s3p413py

1 is shown with the "ollowing

s!ccessive ionisation energies#

&ere the big E!mp comes a"ter the "o!rth electron has been removed. The

"irst 7 electrons are coming "rom the 3rd shell orbitalsH the "i"th "rom. ilicon

is there"ore in gro!p IF

To try on yo!r own

Dec%de h%ch gr"/p a! at"m %s %! %# %t has the #"ll"%!g s/ccess%-e

%"!%sat%"! e!erg%es

END O6 ATOMIC STRUCTURE

'tomic tr!ct!re page 1A o" 0



4"rsheet

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Documents

Unit 1 Mod 1 Atomic Structure and Periodic Table (1)