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8/8/2019 Chapter 4b Group 18
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Group 18 ElementsGroup 18 Elements
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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.
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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
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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.
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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.
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Increases when going down G18.Increases when going down G18.
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..
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DensityDensity
Increases when going down G18.Increases when going down G18.
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.
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SolubilitySolubility
All noble gases areAll noble gases are insolubleinsoluble inin
water.water.
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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.
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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
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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.
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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).).
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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.
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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.
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When facing the tide of difficulties, be determined &
persevere; do not let yourself
be swept away.
~ Still Thoughts