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Atomic Structure &Ions
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ATOMICSTRUCTURE
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Ever wondered if you need to cut a piece of rock into its
smallest possible sie! w"at will it be like#
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ATOMSDefinition: Smallest particles that make up an
element.
Inside the atom, there are 3 types of sub-atomic
particles.
~ $rotons
~ %eutrons~ Electrons
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Arrangement of Particles in an Atom
+
Nucleus
++
+
+
Electron Shells
Key:
Neutron
Proton
Electron
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&efinin' Atoms The Greek philosopher Democritus !"# $.%. &
3'# $.%.( )as amon* the first to su**est thee+istence of atoms from the Greek )ordatomos(
e belie/ed that atoms )ere indi/isible andindestructible
is ideas did a*ree )ith later scientifictheory, but did not e+plain chemical beha/ior,and )as not based on the scientific method &but 0ust philosophy
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T"e (istory in )rief1805 John Dalton - Atomic Theory
1897 JJ Thompson - finds electrons
1909 E Rutherford - discoers protons
1911 E Rutherford - discoers nucleus
191! "iels #ohr - e- are in shells around nucleus
19!$ J %had&ic' - proes e(istence of neutrons
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!
&alton*s T"eory of Atom1( 2ll elements are composed of
tiny indi/isible particles calledatoms( 2toms of the same element are
identical. 2toms of any one
element are different fromthose of any other element.
3( 2toms of different elements combine in
simple )hole-number ratios to formchemical compounds!( In chemical reactions, atoms are combined,
separated, or rearran*ed & but ne/er
chan*ed into atoms of another element.
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"#
&iscovery of ElectronIn 1897, J.J. Thomson used a cathode ray
tube to deduce the presence of a negativelycharged particle: the electron
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Mass of Electron1916 !o"ert #illi$an determines the mass
of the electron: 1%18&' the mass of ahydrogen atom( has one unit of negative
charge
The oil drop apparatus
#ass of the
electron is9.11 ) 1'*+8 g
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4elati/e 5asses of Sub-atomic 6articles
-T!/ 0!/T/
A $roton an% a neutron a'e
a$$ro(imately te same mass)
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--2T!/
0!/T/
4elati/e 5asses of Sub-atomic 6articles
The mass of an electron is 1%18&' of the mass of aproton.
The mass of an electron is almost negligi"le.
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Sub-atomic
Particle
RelativeMass
RelativeElectric
Charge
Found in
Proton
Neutron
Electron
*eca$
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Sub-atomic
Particle
RelativeMass
RelativeElectric
Charge
Found in
Proton 1 +1 nucleus
Neutron 1 0 nucleus
Electron 1/1!0 -1electronshells
*eca$
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*eca$
."2
6
,e atom is .ar-on
/ass num-er 0 "21
atomic num-er 0 6
um"er of protons 6
um"er of electrons 6
um"er of neutrons 1+ 6 6
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"!
*eca$
Al27
"3
,e atom is Aluminium
/ass num-er 0 271
atomic num-er 0 "3
um"er of protons 1
um"er of electrons 1
um"er of neutrons +7 1 1&
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2#
o you no4 4y
If you loo at a $erio%ic
ta-le te atomic mass of
an element is rarely a
4ole num-er)
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Isoto$es
Isoto$es are atoms of te same element
4it te same num"er of protons -ut
different num"er of neutrons/ost elements tat occur commonly are
ma%e u$ of isoto$esEg y%rogen car-on an% clorine
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Isoto$es of y%rogen
http://eqseis.geosc.psu.edu/~cammon/HTML/Classes/PhysicalGeology/Notes/Chapter0/!sotopes.gi"
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Isoto$es of .ar-on
http://encarta.msn.com/media#$%&'('()/!sotopes#o"#Car*on.html
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2tomic masses are calculated by fi*urin* outho) many atoms of each type are there inthe uni/erse.
7or carbon, there are a lot of %-1,less of %-13, and a fe) %-1! atoms.
8hen )e a/era*e out all the masses,)e *et a number that is a little bit hi*her
than 1. The mass for % element is actually 1.#11.
Since )e ne/er really kno) )hich % atom )e are usin*in calculations, )e should use the mass of an a/era*e
% atom.
*elati'e Atomic /ass 8Ar 9
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*elati'e Atomic /ass 8Ar 9
+elati,e atomic mass o" an element isde"ined as the ratio o" the a,erage mass o"an atom to &/&th the mass o" a &C atom
,erage ,alue calculated "rom therelative abundance o" isoto#es o" anelement
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*elati'e Atomic /ass 8Ar 9
ample: Chlorine1 2hich eistsnaturally in t2o isotopic "orms Cl and Cl
$%
1&$&
1&
$%Cl $&Cl
Mass num*er (' ()
Percentage )'3 '3
+elati,e atomic
mass 4r5 4(' )'/&005 6 4() '/&005
7 ('.'
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ill Isoto$es
a'e te same cemical $ro$erties; -. Isoto$es a'e te same cemical
$ro$erties
a'e te same $ysical $ro$erties;/. Isoto$es a'e sligtly %ifferent
$ro$erties
f
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Types of Isotopes 5any elements ha/e isotopes9 only a fe) do not:
e.*. fluorine, sodium, aluminium iodine
$ut artificial ones can be made
main types of isotopes: radioacti/e and non+radioactive
4adioacti/e ones are unstable
;on radioacti/e ones are stable
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3#
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U f I
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Uses of Isotopes(istory &atin'
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,e Atomic Structure
7p
7n
Electronic configuration is 25
N14
7
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element6roton
number
% " S 1"
; ' %l 1'
@ A 2r 1A
7 B C 1B
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element6roton
number
.A.>
% " .! S 1" .A."
; ' .> %l 1' .A.'
@ A ." 2r 1A .A.A
7 B .' C 1B .A.A.1
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Aluminium Electron arran'ement 2 3! 4! 5T"ere are 5 outermost electrons6
T"ese 5 electrons will take part inc"emical reactions6
7"y is aluminium placed in 8roup III oft"e $eriodic Table#
,e Atomic Structure
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6eriodic Table of
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3!
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Gas Symbolelectron
confi*uration
elium e
;eon ;e .A
2r*on 2r .A.A
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>ormation of ions
4n atom: is electrically neutral te num-er of electrons is te same as te
num-er of $rotons
4n ion:
is a charged atom electrons are eiter a%%e% or taen a4ay froman atom
te num-er of electrons is N?, te same as
te num-er of $rotons
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Positi'e ion
electrons are removed from an atom
te atom as more protons tan electrons
it as an overall positive charge
Na
Sodium atom 2, 8, 1
Na
+
Sodium ion, 2, 8
:ose ; e+
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electrons are added to an atom
te atom as more electrons tan $rotons
it as an overall negative charge
O
Oxygen atom 2, 6
O
Negati'e ion
2-
Oxide ion 2, 8
8ain 3e+s
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>ormation of Ions
Atoms @ lose @ electrons to form cations @ Atoms @ gain @ electrons to form @@@@@@@
,e outermost electron sells of ions are
@ completely filled @
y %o atoms gainlose electrons;
So as to acie'e @ sta"ility @ -y a'ing a @ completely filled valence electron
shell sta-le no-le gas @ configuration)
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Ta$e home
An atom B can -e 4ritten in sym-ol form um"er of electrons um"er of protons ;
um"er of neutrons 4 * ;
Atoms missing or a'e e(tra electrons
Ions
Atoms missing or a'e e(tra neutrons
Isoto$es
<4
;
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8hich statement about an atom is trueE
2 2ll the elements ha/e only one nucleon mass(number.
$ The nucleon mass( number can be less thanthe proton atomic( number.
% The nucleon mass( number can be eFual to theproton atomic( number.
D The number of neutrons ne/er eFuals thenumber of electrons.
,est Courself
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!
T"e table s"ows some information about two ions!
and C6
ion protons neutrons electrons
;< 3- ;4
C 3; 3= ;4
7"at are and C#
2 positive ions of different elements$ positive ions of t"e same element
% ne'ative ions of t"e same element
D ne'ative ions of different elements
,est Courself
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5#
Complete t"e followin' table6 >5?
6article
;ucleon
number
ofelement
6roton
number
ofelement
;umber of
electrons protons neutrons
Sodium
atom35 ;;
5a*nesiumion
3@ ;3
7luoride ion < ;-
,est Courself
4toms of an -lement
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5"
4toms of an -lement
8u*9atomic particles
consists o"
contains
Protons lectronsNeutrons
Protonnum*er
Nucleonnum*er
lectroniccon"iguration
!sotopes
determinestogether mae up
determines
ha,e the same num*er o"
+elati,e atomic mass
ha,edi""erentnum*ers o"
determine
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