atomic structure (chemistry o level)

8/19/2019 Atomic Structure (Chemistry O Level)

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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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"2

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 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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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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2!

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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3


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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

atomic structure (chemistry o level)

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