chapter 4b group 18

8/8/2019 Chapter 4b Group 18

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Group 18 ElementsGroup 18 Elements



HeliumHelium

Neon Neon

ArgonArgon

KryptonKrypton

XenonXenon

RadonRadon

Group 18 elements areGroup 18 elements are

known as noble gases.known as noble gases.

Air consists of Air consists of

approximately 1 % of approximately 1 % of noble gases.noble gases.



Physical PropertiesPhysical Properties

ElemeEleme

ntnt

ProtonProton

number number

AtomicAtomic

radiusradius

MPMP

((ºC)ºC)

BPBP

((ºC)ºC)

PhysicalPhysical

statestate

DensityDensity

(g dm(g dm--33))

HeHe 22 0.0500.050 -- 270270 -- 269269 GasGas 0.170.17

Ne Ne 1010 0.0700.070 -- 248248 -- 246246 GasGas 0.840.84

Ar Ar 1818 0.0940.094 -- 189189 -- 186186 GasGas 1.661.66

Kr Kr 3636 0.1090.109 -- 156156 -- 152152 GasGas 3.453.45

XeXe 5454 0.1300.130 -- 112112 -- 107107 GasGas 5.455.45



Atomic radius ( atomic size )Atomic radius ( atomic size )

Increases when going down G18.Increases when going down G18.

Because theBecause the number of shellsnumber of shells

occupied with electrons increasesoccupied with electrons increases

down the group.down the group.



Melting & Boiling PointsMelting & Boiling Points

RelativelyRelatively lowlow ± ± because noble gases because noble gases

made up of made up of single atomssingle atoms heldheld

together bytogether by weak van der Waalsweak van der Waalsforces of attractionforces of attraction. Only. Only smallsmall

amount of heat required to overcomeamount of heat required to overcome

the forces of attractionthe forces of attraction duringduring

melting & boiling.melting & boiling.




Atomic size increasesAtomic size increases down thedown the

group. Thus,group. Thus, van der Waals forces of van der Waals forces of

attractionattraction between atoms become between atoms becomestronger.stronger. More heat energy isMore heat energy is

required to overcome the stronger required to overcome the stronger

forces of attraction during melting &forces of attraction during melting & boiling boiling..



DensityDensity


because the increase in atomic mass because the increase in atomic mass

is bigger as compared to the increaseis bigger as compared to the increase

in volume.in volume.



SolubilitySolubility

All noble gases areAll noble gases are insolubleinsoluble inin

water.water.



Electrical & Heat ConductivityElectrical & Heat Conductivity

All noble gases :All noble gases :

cannot conduct electricity.cannot conduct electricity.

Poor conductor of heat.Poor conductor of heat.



Unreactive properties of noble gasesUnreactive properties of noble gases

ElementElement Electron arrangementElectron arrangement

HeHe 22

Ne Ne 2.2.88

Ar Ar 2.8.2.8.88

Kr Kr 2.8.18.2.8.18.88

XeXe 2.8.18.18.2.8.18.18.88

RnRn 2.8.18.32.18.2.8.18.32.18.88



HeliumHelium atom has only 1 filledatom has only 1 filled

electron shell. It has 2 electrons. Thiselectron shell. It has 2 electrons. This

electron arrangement is called theelectron arrangement is called the

duplet electron arrangement.duplet electron arrangement. The outermost shells of other nobleThe outermost shells of other noble

gases have 8 electrons, called thegases have 8 electrons, called the

octet electron arrangement.octet electron arrangement.



Both the duplet & octet electronBoth the duplet & octet electron

arrangement arearrangement are very stablevery stable. Hence,. Hence,

atoms of noble gases do not releaseatoms of noble gases do not release

electrons, accept electrons or shareelectrons, accept electrons or shareelectrons with other atoms.electrons with other atoms.

Thus, noble gases exist asThus, noble gases exist as monomono--

atomsatoms && inert chemicallyinert chemically ( unreactive( unreactive).).



Uses of G18 elementsUses of G18 elements

HeliumHelium

Used to fill weather balloon &Used to fill weather balloon &

airships.airships.

Light & nonLight & non--flammable.flammable.



Neon Neon

advertising light bulbsadvertising light bulbs ± ± reddish orangereddish orange

colour.colour.

ArgonArgon electric bulbselectric bulbs ± ± argon is chemically inert,argon is chemically inert,

thus prevent hot tungsten filament fromthus prevent hot tungsten filament from

being oxidised. being oxidised. Welding. Argon prevent hot metals fromWelding. Argon prevent hot metals from

reacting with Oreacting with O22 in the air.in the air.



When facing the tide of difficulties, be determined &

persevere; do not let yourself

be swept away.

~ Still Thoughts

chapter 4b group 18

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