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7/28/2019 Group18-1-17


7/28/2019 Group18-1-17


Arrangement of Elements in The

Periodic Table

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7/28/2019 Group18-1-17


Question 1 :

The Melting Point and Boiling

Point increases down the Group18. Why?

Atomic size increases Forces of attraction between atoms

become stronger

More heat energy is needed

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Question 2 :


Point of Group 18 elements are

very low (negative) generally.

Why?

Van der Waals force between atoms

are weak

Less heat energy is needed to

overcome the force

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Question 3 :

All elements in Group 18 are said

to be not reactive (Inert). Why?

The valence shells are fully filled with

8 electrons (except He)

Achieve octet (duplet) electron

arrangement

Not tend to release, receive or shareelectrons with other elements.

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Question 4 :

Density of Group 18 elements

increases down the group. Why?

The increase rate of atomic massis higher than the rate of atomic

size.

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The Inert nature of Group 18

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Group 1 – Alkali Metals

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Question 1 :


Point decreases down Group 1.Why?

Atomic size increasesMetallic bond between atoms become

weaker

Less heat energy is needed

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Question 2 :Define “electropositivity”.

The tendency of one atom todonate its valence electrons

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Question 3 :

The reactivity of alkali metalsincreases down the group.

Why?

Atomic size increasesDistance of valence e from nucleus is

further

Attraction between nucleus and

valence e is weaker

Easier to donate the single valence e

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Question 4 :

Potassium is more reactivethan sodium. Why?

Atomic size of K is bigger Distance of valence e from nucleus of

K is further

Attraction between nucleus andvalence e of K is weaker

Easier for K to donate the singlevalence e

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Question 5 :

Alkali metals conduct

electricity in solid phase.

Why?

Atoms contain free movingelectrons

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Summary

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Guestion 6:

Alkali metals are stored in pariffinoils. Why?

The metals are very reactiveTo prevent them from being

oxidized by oxygen and wet

air

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Chemical Properties

Alkali metals1) Reaction with water

2) Reaction with oxygen

3) Reaction with chlorine gas

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Reaction with water

2Li(s) + 2H2O(l) 2LiOH(aq) + H2(g)

2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

2K(s) + 2H2O(l) 2KOH(aq) + H2(g)

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Observations

Reaction with water - Lithium

2Li(s) + 2H2O(l) 2LiOH(aq) + H2(g)

• floats and move rapidly and randomly• Hissing sound (fizzing)

• Dissolved into water

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Observations

Reaction with water - Sodium

2Na(s) + 2H2O(l) 2NaOH(aq) + H2(g)

• turns into sphere• floats and move faster

• small yellow flame

• Hissing sound (fizzing)• Dissolved into water

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Observations

Reaction with water - Potassium

2K(s) + 2H2O(l) 2KOH(aq) + H2(g)

•

turns into sphere• floats and move very fast

• burns in lilac flame

• Hissing sound (fizzing)

• Dissolved into water

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Gas test : burning splinter

Hydrogen gas:

Collect the gas into a test tubeApproach the burning splinter towards the

mouth of test tube

“pop” sound occurred

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alkali test : Red litmus

Alkali aka LiOH, NaOH, KOH :

Put some solution onto a glass discDip the red litmus into the liquid

It turns blue

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Reaction with oxygen

2Li(s) + O2(g) 2Li2O(s)

2Na(s) + O2(g) 2Na2O(s)

2K(s) + O2(g) 2K 2O(s)

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Observation

Lithium + oxygen

Burn in red red flame

White solid (lithium oxide)

Li2O dissolves in water

2Li(s) + O2(g) 2Li2O(s)

Li2O(s) + H2O(l) 2LiOH(aq)

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Observation

Sodium + oxygen

Burn brighter in red yellow flame

White solid (sodium oxide)

Na2O dissolves in water

2Na(s) + O2(g) 2Na2O(s)

Na2O(s) + H2O(l) 2NaOH(aq)

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Observation

Potassium + oxygen

Burn in red lilac flame

White solid (potassium oxide)

K2O dissolves in water

2K(s) + O2(g) 2K 2O(s)

K2O(s) + H2O(l) 2KOH(aq)

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Reaction with chlorine

2Li(s) + Cl2(g) 2LiCl(s)

2Na(s) + Cl2(g) 2NaCl(s)

2K(s) + Cl2(g) 2KCl(s)

The salts produced here are soluble in water

http://localhost/var/www/apps/conversion/tmp/scratch_11/Na+Cl.MOV










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Group 17 - Halogen

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Group 17

HalogenHalogen

In CCl4

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THE DANGERS OF HALOGENS

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Physical Properties Of Halogens

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Physical Properties of Halogens

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Summary

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Physical Properties Of Group 17

4.94Grey solid184114Iodine

3.14Brownish

Liquid

59-7Bromine

0.003Pale

Green gas

-35-101Chlorine

0.0016Pale yellow

gas

-188-220Fluorine

Density/

G dm-3

Appearance

Boiling

Point/ oC

MeltingPoint / oC

Element

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Summary of Physical Properties

Physical state : gas liquid solid

Low melting and boiling point

Do not conduct electricity

Poor heat conductor

Low density

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Question 1 :


Point increases down Group 17.Why?

Molecular size increases

Forces of attraction between

molecules become stronger

More heat energy is needed

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Question 2 :

Halogens do not conduct

electricity . Why?

The particles of halogens are

molecules

They have no free ions

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Chemical Properties

Halogens1) Reaction with water

2) Reaction with Iron

3) Reaction with alkali

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Observations

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1) Reaction with water

I2(g) + 2H2O(l) HI(aq) + HOI(aq)

Br2(g) + 2H2O(l) HBr(aq) + HOBr(aq)

Cl2(g) + 2H2O(l) HCl(aq) + HOCl(aq)

Name : HOCl = hypochlorus acidHOBr = hypobromus acid

HOI = hypoiodus acid

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2) Reaction with iron

2Fe(s) + 3Cl2(g) 2FeCl3(s)

Name : FeCl3 = Iron(III) chlorideAll the salts produced are soluable in

water

2Fe(s) + 3Br2(g) 2FeBr3(s) 2Fe(s) + 3I2(g) 2FeI3(s)

http://localhost/var/www/apps/conversion/tmp/scratch_11/Iron%20with%20Cl2.swf

http://localhost/var/www/apps/conversion/tmp/scratch_11/Iron%20with%20Cl2.swf

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How to draw the diagram of Iron

being burned in halogens

Heating

Potassium permangate + HCl

Chlorine gas

Iron wool

Soda chalk

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How to draw the diagram of Iron

being burned in halogens

HeatingHeating

Brominegas

Heating

Bromine water

Iron wool

Heating

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3) Reaction with alkali

NaOH(aq)+Cl2(g) NaCl(aq)+NaOCl(aq)+H2O(l)

Name : NaOCl = sodium chlorate(I)NaOBr = sodium bromate(I)

NaOI = sodium iodate(I)

NaOH(aq)+Br2(g) NaBr(aq)+NaOBr(aq) + H

2O(l)

NaOH(aq)+I2(g) NaI(aq)+NaOI(aq)+ H2O(l)

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Summary 1

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Summary 2

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Question 3 :

The reactivity (electronegativity)

of halogens decreases down the

group. Why?

Atomic size increasesDistance of valence e from nucleus is

further

The strength to attract one electron

into valence shell is weaker

Harder to attract electron

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Question 4 :

Define “electropositivity”.

The tendency of one atom toattract electrons into the

outermost occupied shell

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group18-1-17

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