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CHEMISTRY MODUL PEMBELAJARAN

CHAPTER 4 : THE PERIODIC TABLE OF ELEMENTS

A Historical Deelo!"e#t O$ T%e Perio&ic Ta'le

( A#toi#e Laoiser (1743-1794)

The first Scientist classifies substances including light and heat, into metals and non-

metals.

Substances were classified into $o)rgrous with si"ilar c%e"ical !ro!erties.

!is classification was unsuccessful because light, heat and a few other comounds

were also considered as elements.

2 Jo%a## Do'erei#er (17"#-1"49)

$i%ided the elements into *ro)!s o$ t%ree ele"e#ts with si"ilar c%e"ical

!ro!erties, &nown a $obreiner's triads.

The atomic mass of the middle element was aroimatel the a%erage atomic mass

of the other two elements in each triad.

This classification led chemist to realise that there was a relationshi between the

chemical roerties and the atomic mass of each element.

Example*

Ele"e#t i# tria& +i Na

Average relati%e

atomic mass of +i

and

Relative atomicmass, Ar

7 39 2

397 +

+,

, Jo%# Ne-la#&s (1"37-1"9") CHAPTER 4 * THE PERIODIC TABLE OFELEMENTS

1

?

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!e arranged the &nown elements in order of i#creasi#* ato"ic "ass.

lements with si"ilar c%e"ical !ro!ertieswere reeated at eer. ei*%t% ele"e#t.

This was &nown as the +aw of /cta%es.

This sstem was inaccurate because the +aw of /cta%es was obeed b the first 17

elements onl and there were some elements with wrong atomic mass0mass number.

!owe%er, ewlands was the first chemist to show the e/iste#ce o$ a !erio&ic !atter#

for the roerties of elements.

4 Lot%ar Me.er (1"3#-1"92)

!e lotted a *ra!% o$the atomic %olumea*ai#st t%e ato"ic "assfor all the &nown

elements.

tomic %olume

!e realised that elements with similar chemical roerties occ)!ie& equivalent

positionsalo#* t%e c)re.

!e was successful in showing that t%e !ro!erties o$ t%e ele"e#tsformed a eriodic

attern against their atomic masses.

CHAPTER 4 * THE PERIODIC TABLE OFELEMENTS

2

Mass of 1 mol (g)

Density (g cm-3)

Li

Atomic

volume

Atomic mass

Na

K

Be

Mg

Ca

B

Al

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0 Di"itri Me#&elee (1"34-19#7) rranged the elements in order of increasing atomic masses.

!e groued the elements according to similar chemical roerties.

lements with similar chemical roerties were in the same grou5.

!e left gas in the table to be filled b undisco%ered elements.

!e was able to redict the roerties of undisco%ered elements.

e.g* &asilicon, Esis redicted b 6endelee% in 1"9 was disco%ered as

8ermanium, 1ein 1"" 5.

2 He#&r. J3 13 Mosele. (1""7-1912) Studied the -ra sectrum of elements.

:ntroduced the concets ofproton numberof each elements5

!e concluded that roton number should be used as the basis for the eriodic changes

of chemical roerties of elements instead of the atomic mass.

!e rearranged the elements in order of i#creasi#* !roto# #)"'erin the ;eriodic

Table.

B Arra#*e"e#t o$ Ele"e#ts i# t%e Perio&ic Ta'le

lements in the ;eriodic Table are arranged in an increasing order of roton number,

ranging from 1 to 11

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There are ==== %orio#tal ro-sof elements in the ;eriodic Table.

ach of these hori>ontal rows of elements is called a========

The hori>ontal rows are &nown as =====. to======.

Activity 1*-

:n the table below, write *

(a) 8rou 1 to 1"

(b) ;eriod number 1 to 7

H HeLi Be

B C N O F Ne

Na M* Al Si P S Cl Ar

5 Ca

+anthanides

ctinides

The number of valence electronsin an atom decides the =====..==== of anelement in the ;eriodic Table.

Example*

The roton number of sodium, a is 11.

The electron arrangement of sodium atom is

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?or elements with (and +%alence electrons, the group#)"'erof the element is t%e

#)"'er o$ ale#ce electro#sin its atom.

?or elements with , to6%alence electrons, the group#)"'erof the element is t%e

#)"'er o$ ale#ce electro#sin its atom lus ten (7(8) %alence electron @ 1# 5

Example*

The roton number of chlorine is 17

The electron arrangement of chlorine is

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Example*

The roton number of magnesium is 1 ca##ot co#&)ct electricit.and !oor co#&)ctors o$

%eat3

1oi#* &o-# 8rou 1" Re"e! t# Text B##$% page45

Ele"e#t

Relatie

ato"ic

"ass

Proto#

#)"'er

Ato"ic

ra&i)s

(nm)

Melti#*

!oi#t

(#C)

Boili#*

!oi#t

(#C)

De#sit.

(g m&')

!elium> He 4 Ne Ar 4# 1"

rton> 5r "4 3

enon> ?e 131 24

Hadon> R# e increases as the number of shells in the atom increases from !elium to

Hadon.

The melting and boiling oints is %er low.

because the atoms of oble gases are attracted b wea& force.

+ess energ is reEuired to o%ercome.

!owe%er, the melting and boiling oints i#creases when going down 8rou 1".

because the atomic si>e of each element i#creasesdown the grou,

the forces of attraction between the atoms of each element become stro#*er

thus "ore e#er*.is reEuired to o%ercome the stronger forces of attraction during

melting or boiling.

The densit of an element increases down the grou because the atomic mass of each

element is increases.

T%e I#ert Pro!ert. o$ 1ro)! (6 Ele"e#ts

ll oble gases are inert which means c%e"icall. )#reactie.


1

!ncrea$e$

!ncrea$e$

!ncrea$e$

!ncrea$e$

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oble gases and the electron arrangement of their atoms.

No'le *as Electro# arra#*e"e#t

!elium e i#creasesbecause the number of shells increases.

The densit increases because the increasing in atomic massis faster than the

increasing in atomic %olume0si>e.

The melting and boiling oints &ecreasesbecause when the atomic si>e increases, the

metal bond between the metal atoms becomes wea&er.

The hardness of the metal &ecreases.

C%e"ical Pro!ertiesof 8rou 1 elements *

(a) Heact with -aterto roduce al&aline metal hdroide solutions c#l#(!le))

)#l(ti#n)5 and released hdrogen gas.

Metal O'seratio#

Li

+ithium mo%es slowlyon water surface with hiss&sound.

The colourless solution formedI turns re& litmus aer to 'l)e.

Na

Sodium mo%es quic'lyon water surface with Lhiss&sound.

The colourless solution formedI turns re&litmus aer to 'l)e.


13

al*ali

N)cleo# #)"'er

water

metal*

e'litmus %a%er

turns(luee'litmus %a%er

eaction(ec

ome$

more+igorou$

eacti+it,in

cr

ea$e$

Metal -1 . H2" / metal %,'ro0i'e . H,'rogen ga$

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5

;otassium mo%es vigorouslyon water surface with Lhiss&

sound.

The colourless solution formedI turns re&litmus aer to 'l)e.

(hemical equation*

++i @ +!

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Metal O'seratio#s

Li

+ithium burns slowlywith a re&flame.

white0 fume solid is roduced.

Na

Sodium burns brightlywith a .ello-flame.

whitesolid is roduced.

5

;otassium burns very brightwith a !)r!lelilac

flame.

whitesolid is roduced.

(hemical equation*

4+i @ /

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Ele"e#ts O'seratio#s

Li+ithium burns slowlywith a re&flame.

-%ite soli&is roduced.

Na

Sodium burns brightlywith a .ello-flame.


5

;otassium burns very brightwith a !)r!le

flame.


++i @ Al

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+a @ Al

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it is easier for the atom to donate the single %alence electron to achie%e the

sta'leoctet0dulet electron arrangement of the atom of oble gases.

Heacti%it increaseswhen going down the grouM

Activity 4 *-

1. Table below shows the electron arrangements of element D, and N.

rrange the elements in ascendingorder of reacti%it.

Ele"e#t Proto# N)"'er Electro#

Arra#*e"e#t

@ 11

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E 1ROUP (9 ELEMENTS

1. The s."'olof elements in 8rou 17.

?luorine Ahlorine Fromine :odine statine

Ti!s : Met%o& to "e"orise t%e *ro)! (9s ele"e#ts


19

) Cl Br ! At

'l

r

)lora

Canti$

Bumi

!n&a

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(i%) !alogen ha%e low melting and boiling oints because their molecules are

attracted to each other b wea& inter-molecular forces. (,an e! -aal) "#!ce*

force of attraction between molecules).

(%) Dhen going downthe grou, the melting and boiling oints i#creases .This is because *

the molecular si>e i#creases .

?orces of attraction between molecules becomes stro#*er

eed "oreenerg to o%ercome the forces of attraction between molecules.

the melting and boiling oints i#creases.

=3 C%e"ical Pro!erties

(a) Heact with -aterto roduce t-oacids.

Example*

Al solution e@ibits (leac%ing %ro%erty

HBr H"Br

H,'ro(romic aci' H,o(romu$ aci'

Bromine

ater

ater

Heat

!o'ine

(soli&)

ater

Heat

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+/! @ Al< Al @ /Al @ !

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Ahemical roerties of all elements are t%e sa"ebecause the number of %alenceelectrons are the same and attain0achi%e the oble gas arrangement in a similar wa.

1#. Reactiit.of 8rou 17 elements *

Dhen going down8rou 17,

the roton number are i#creases

the number of shells occuied with electrons are i#creases

the atomic si>e of atoms are i#creases

the outermost occuied shell of each halogen atoms becomes $)rt%erawa

from the nucleus.

the nuclei attraction forces to attractone electron into the outermost occuied

shell b the nucleus becomes wea&er

it is harder for the atom to attractone electron to achie%e sta'leoctet0dulet

electron arrangement of the atom of oble gas.

The strength of halogen atom to attract electron decreasefrom ?luorine to

statine Electro#e*atiit.decreases5

this causes the reacti%it decreasesdown the grou.

cti%it 2 *-

(

Jnderline the answer.

Ahlorine, bromine and iodine ha%e 10

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The atomic si>e i#creases&ecreases down the grou.

The distance of the outermost shell becomes *reater#earerfrom the nucleus.

The force of attraction of the nucleus on the electrons of the outermost shell

i#creases&ecrease.

The tendenc of an atom to recei%e o#et-ot%reeelectron to achie%e an octet

electron arrangement i#creases&ecrease .

,

The e*planation==

Jnderline the correct answer.

The atomicsieof flourine is s"aller'i**erthan chlorine.

The $orce o$ attractio# 'et-ee# #)cle)sof fluorine atom and ale#ce electro#s

are stro#*er-ea;er.

?luorine atom can acce!treleaseelectron easil.

Sa$et. !reca)tio#s i# %a#&li#* 1ro)! (9 ele"e#ts

1. The %aour of flourine, chlorine and bromine are.!oiso#o)s

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(a) Dhat is the %alence electron of the elements , N and QG

===================================

(b) Dhich grou in the eriodic table can ou find the elements , N and QG

===================================

(c) lement N can react with water.State t-ochemical roerties of the solution roducedG

(d) Falance the eEuation for the reaction between element Q and hot iron.

===================================

+3 (a) +ist all halogen elements from the to to the bottom of 8rou 17.

======================================.

(b) Dhich are the most reacti%e and least reacti%e halogenG

6ost reacti%e * ==========, least reacti%e * ============

,3 Aomlete the chemical eEuations for the following reaction *

(a) Ahlorine with water * ====================...

(b) bromine with iron * ====================...

(c) iodine with sodium hdroide * ====================...

43 lain the changes to the reactivityof halogens when going down 8rou 17.Jnderline the correct answer.

The atomic si>e of halogen i#creases&ecreasesdown the grou.

The distance of the outermost shell becomes #earer$)rt%er from the

nucleus.

Therefore, the force of attraction b the nucleus on the electrons in the

outermost shell becomes -ea;erstro#*er


26

Fe 7 K+ FeK,

1. Heact with metal, roduced ==.. and =====. gas.

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The tendenc of an atom to receieacce!t o#eelectron to achie%e an octet

electron arrangement decrease.

This causes the reacti%it i#creases 0 &ecreases down the grou.

03 lain the changes to the electronegativityof halogens when going down 8rou17.Jnderline the correct answer.

The atomic si>e of halogen &ecreasesi#creasesdown the grou.

The distance of the outermost shell becomes #earer$)rt%erfrom the

nucleus.

Therefore, the force of attraction b the nucleus on the electrons in the

outermost shell becomes -ea;erstro#*er

The tendenc of an atom to receieacce!t*ai#o#eelectron to achie%e an

octet electron arrangement decrease.

This causes the electronegati%it i#creases 0 &ecreases down the grou.

F ELEMENTS IN A PERIOD

Pro!erties o$ ele"e#ts i# Perio& ,

Ele"e#t o$ Perio& , Na M* Al Si P S Cl Ar

Proto# #)"'er 11 1< (, (4 (0 (2 (9 1"

Electro#arra#*e"e#t

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Electro#e*atiit.

Electro!ositiit.

The trends of changes acrossPerio& , ("!#m leftt# right)

1. The roton number i#creasesb o#eunit from one element to the net element.

e of atom of the elements decrease.

This is due to i#creasi#*of nuclei attraction force on the electrons.

2. The electronegati%it of elements i#creases

This is also due to the i#creasi#*of the nuclei attraction force on the electrons in

the outermost shell an the decreasing in atomic si>e.

. ll the elements in ;eriod 3 eist as soli&s ecet chlorine and argon which are

*ases3

ACID

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cidic oides reacts with al;alisto form saltand -ater.

Example*

S/

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cti%it 7 *-

( Table below shows the smbol of element, roton number and atomic radius ofelements in ;eriod 3.

Ele"e#t Na M* Al Si P S Cl Ar

Proto# #)"'er 11 1< 13 14 12 1 17 1"

Ato"ic ra&i)s #.12 #.13 #.1

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(d) Table below shows the smbol of oide comound when the elements in eriod 3 arereacted with ogen.

a

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@3 i3@ i(/3)3

(oloured ons or(ompounds

The colours of some aEueous solutions of ions of transition elements *

Na"e o$ Io#of transition element

For")la o$ Io#of transition element

Colo)rin aEueous solution

Ahromate ion Ar/4

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cti%it " *-

( ?igure 1 below shows art of the ;eriodic Table of lements.

H He

O

M* Al

?:8JH 1

Fased on ?igure 1 abo%e, answer the following Euestions *

(a) Dhat is the element reresented b the smbol FeG

==============================

(b) :n figure abo%e, mar& L?' in the boes for all the transition element.

(c) State o#esecific characteristic of transition element.

==============================

(d) Drite the electron arrangement for the M*atom

==============================

(e) Falance the chemical eEuation for the reaction between aluminium andogen gas.

==============================

(f) Fased on the abo%e informations, which gas is more suitable to be used inmeteorological balloonsG8i%e one reason.

==============================

==============================


33

Helium -a$

li-t

not rea0ti/e

0olourless

H,'rogen -a$

li-t

flammable

0olourless

e

l @ /

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+ Table < shows the roton numbers of element ;, , H, S and T.

Ele"e#t Proto# #)"'er Electro# arra#*e"e#t

; 3

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B !enr 6osele D Uohann $obereiner

, Dhich of the following elements are in 8rou 1 in the ;eriodic Table of lementsG

A Sodium and otassium

B +ithium and magnesium

C !drogen and helium

D !elium and neon

4 Dhich of the following elements are in 8rou 1" of the ;eriodic Table of lementsG

A !elium and &rton

B !drogen and ogen

C /gen and &rton

D !elium, hdrogen and ogen

0 Dhich of the following diagrams reresents the electron arrangement of an elementof 8rou 17G

A C

B D

END OF CHAPTER 4

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capter 4

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