Chapter 4c Group 1 Elements

8/8/2019 Chapter 4c Group 1 Elements

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Group 1 ElementsGroup 1 Elements


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Physical PropertiesPhysical Properties

ElementElement ProtonProton

numbernumber

AtomicAtomic

radiusradius

(nm)(nm)

MPMP

(C)(C)

BPBP

(C)(C)

DensityDensity

(g cm(g cm--33))

ElectronegativityElectronegativity

LiLi 33 0.150.15 181181 13471347 0.530.53 1.01.0

NaNa 1111 0.190.19 9898 886886 0.970.97 0.90.9

KK 1919 0.230.23 6464 774774 0.860.86 0.80.8

RbRb 3737 0.250.25 3939 688688 1.531.53 0.80.8

CsCs 5555 0.260.26 2828 678678 1.871.87 0.70.7


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All alkali metals areAll alkali metals are

grey solidsgrey solids withwith shiny silvery surfaceshiny silvery surfacewhen freshly cut.when freshly cut.

softsoft solids & can be easily cut.solids & can be easily cut.

havehave low densitieslow densities as compared toas compared toheavy metals.heavy metals.

goodgood conductors of heat & electricityconductors of heat & electricity..

havehave low melting & boiling pointslow melting & boiling points asascompared to heavy metals ( Cu : mpcompared to heavy metals ( Cu : mp1083 C, bp 2567 C).1083 C, bp 2567 C).


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Down the group,Down the group,

Atomic radius Atomic radius

thethe number of shells occupied with e .number of shells occupied with e .

Both mp & bpBoth mp & bp

metallic bondingmetallic bonding between atomsbetween atoms

becomesbecomes weakerweaker,, less heat energyless heat energyrequired to overcome the metallic bondingrequired to overcome the metallic bondingduring melting & boiling point.during melting & boiling point.

density density increase inincrease in atomic mass >atomic mass > increase inincrease involume.volume.

alkali metals become softeralkali metals become softer


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Chemical PropertiesChemical Properties

Very reactiveVery reactive must be kept inmust be kept in paraffin oil.paraffin oil.

Alkali metal + HAlkali metal + H22OO metal hydroxide + H metal hydroxide + H22

2Na + 22Na + 2HH22OO 2NaOH + H 2NaOH + H22

Alkali metal + OAlkali metal + O22 metal oxide metal oxide

4Na +4Na + OO22 2Na 2Na22OO

Alkali metal + ClAlkali metal + Cl22 metal chloride metal chloride2Na + Cl2Na + Cl22 2NaCl 2NaCl


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LiLi burns slowly with aburns slowly with a redred flame.flame.

NaNa burns rapidly & brightly with aburns rapidly & brightly with a

yellowyellow flame.flame.

KK burns very rapidly & brightly with aburns very rapidly & brightly with alilaclilac flame.flame.


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Reactivity of alkali metalsReactivity of alkali metals

Increases down the group.Increases down the group.

LiLi NaNa KK RbRb Cs Fr Cs Fr

more reactivemore reactive

Reactivity is measured by theReactivity is measured by the easeease ofof

its atomits atom to lose its single valenceto lose its single valence

electronelectron to achieveto achieve stable noble gasstable noble gas

electron arrangement (duplet / octet).electron arrangement (duplet / octet).


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LiLi Li Li++ + e+ e--

(2.1)(2.1) (2)(2)

NaNa Na Na++

+ e+ e--

(2.8.1)(2.8.1) (2.8)(2.8)

KK K K++ + e+ e--

(2.8.8.1)(2.8.8.1) (2.8.8)(2.8.8)


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Atomic sizeAtomic size from Li to Fr.from Li to Fr.

Single valence e becomesSingle valence e becomes furtherfurther

awayaway from nucleus.from nucleus.

This cause the single valence e to beThis cause the single valence e to be

moremore weakly pulledweakly pulled by the nucleus.by the nucleus.

Thus, the single valence e can beThus, the single valence e can be

released more easilyreleased more easily down the group.down the group. Reactivity of alkali metals Reactivity of alkali metals down thedown the

group.group.


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Electropositivity of alkali metalsElectropositivity of alkali metals

ElectropositivityElectropositivity is theis the ability to lose eability to lose e

to form positive ion.to form positive ion.

Electropositivity of alkali metalsElectropositivity of alkali metals down the groupdown the group..

Strength as reducing agent Strength as reducing agent downdown

the group.the group.


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Safety precautionsSafety precautions

in handling G1 elementsin handling G1 elements Avoid handling with bare hands.Avoid handling with bare hands.

Wear safety goggles & gloves duringWear safety goggles & gloves during

the experiment.the experiment. Li, Na & K must be kept inLi, Na & K must be kept in paraffin oilparaffin oil..

Rb, Cs & Fr are stored inRb, Cs & Fr are stored in sealedsealed

glass tubesglass tubes to prevent reacting withto prevent reacting with

oxygen & vapor in the air.oxygen & vapor in the air.


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Stopping halfway is, in truth,Stopping halfway is, in truth,more difficult & tiring thanmore difficult & tiring than

persevering on the path towardpersevering on the path towardthe final goal.the final goal.

~ Still Thoughts~ Still Thoughts

Chapter 4c Group 1 Elements

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