chemistry lesson group 17

8/13/2019 Chemistry Lesson Group 17

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Group 7 Elements


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Have you ever seen this object?When did you use it in your daily life?

Do you know the chemical element in it?


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Group 7 Elements

Consists non-metals

elements which are known as

Halogen.

Exist as Diatomic molecules


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Fluorine,F

Chlorine,Cl

Bromine,Br

Iodine,I

Astatine,At


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Exist as

diatomic

molecules at

room

conditions

Do not

conduct

electricity

Low

Density

Pungent

smell and are

poisonous

Very low

melting

points and

boiling points

Physical Properties ofGroup 17 Elements


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Chlorine

Bromine

Fluorine


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Iodine Astatine


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HalogenAtomic

MassMeltingPoint

BoilingPoint

Electro-negativity)

Physical stateat room

temperature

Fluorine 18.998 53.53 85.03 3.98 Pale yellow

Chlorine 35.453 171.6 239.11 3.16

Greenish-yellow

gas

Bromine 79.904 265.8 332.0 2.96Reddish-brown

liquid

Iodine 126.90 386.85 457.4 2.66Purplish-black

solidAstatine (210) 575 610 ? 2.2

Physical Properties of Group 17 Elements


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Change in physical

properties down the groupBrief explanation

The number of shells of the atom

increases.

Atomic radius or atomic size

increases down the group.

Forces of attraction between

particles also increases.

More heat energy is needed to

overcome the forces of attraction

between these particles.

Mass of atom increase

Atomic size increases down the

group

Forces of attraction between

molecules also increase

Ability to receive electrons

decreases down the group.

Atomic radius or size of atom

increases

Melting point and boiling point

of elements increases

Density of elements increases.

Existence of physical states ofelements which are different at

room conditions

Electronegativity decreases


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Chemical Properties of Group 17 Elements

Element Electronarrangement

Number ofvalence

electrons

Fluorine 2.7 7

Chlorine 2.8.7 7

Bromine 2.8.18.7 7

Iodine 2.8.8.18.7 7

Astatine 2.8.18.32.18.7 7

Table: Arrangement of electrons of Group 17

elements.


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Arrangement of electrons ofGroup 17 elements.

2.7 2.8.7


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2.8.18.7 2.8.18.18.7


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2.8.18.32.18.7


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Chemical Properties of Group 17 Elements

Halogen elements such as chlorine, bromine and

iodine show similar chemical properties when reacting

with

WaterIron

Sodium hydroxide solution

Because they have the same number of valenceelectrons which is 7 electrons at the outermost shell.


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The reactivity of halogens decreases down the group

because:

The atomic size increases down the group

The distance of the outermost shell becomes

further from the nucleus

The force of attraction of the nucleus on theelectrons of the outermost shell decreases

The tendency of an atom to receive an electron

to achieve an octet electron arrangement

decreases

F2 Cl2 Br2 I2 At2Decreasing reactivity


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Safety precautions in handlings Group 17 elementsHalogens are elements which are very poisonous andcorrosiveChlorine gas and bromine vapour cause breathingdifficulties and death if inhaled in large quantities.Bromine vapour can cause dizziness, nausea and burns onskin.Thus, halogens must be handled with care:

perform the experiment in a fume chamberdo not inhale halogen gas or vapourdo not touch halogens with bare hands wear gloves)wear safety goggles when handling halogens.


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chemistry lesson group 17

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