Post on 03-Jun-2018
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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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