|
12.1
Physical properties of selected Group 17 elements
|
1
|
Candidates
should be able to:
(a)
state that the colour intensity of Group 17 elements: Cl2, Br2, I2, increase
down the group;
(b)
explain how the volatility of Group 17 elements decreases down the group.
|
|
12.2
Reactions of selected Group 17 elements
|
4
|
Candidates
should be able to:
(a) deduce and explain the relative
reactivities of Group 17 elements as oxidising agents from Eยบ values;
(b)
explain the order of reactivity of F2, Cl2, Br2, I2 with
hydrogen, and compare the relative thermal stabilities of the hydrides;
(c) explain the reactions of chlorine
with cold and hot aqueous sodium hydroxide.
|
|
12.3
Reactions of selected halide ions
|
2
|
Candidates
should be able to:
(a)
explain and write equations for reactions of Group 17 ions with aqueous
silver ions followed by aqueous ammonia;
(b)
explain and write equations for reactions of Group 17 ions with concentrated
sulphuric acid.
|
|
12.4
Industrial applications of halogens and their compounds
|
1
|
Candidates
should be able to:
(a)
describe the industrial uses of the halogens and their compounds as
antiseptic, bleaching agent and in black and white photography;
(b)
explain the use of chlorine in water treatment
|
1 The Group 17 elements (also known as halogens) are fluorine (F), chlorine(Cl), bromine (Br) , iodine (I) and astatine (At).
2
All have seven electrons in their valence shells with the configuration
of ns2 np5.
3
Under normal conditions, they exist as simple diatomic molecules of Cl2, Br2 and I2
through electron sharing.
Element
|
Chlorine
|
Bromine
|
Iodine
|
Atomic radius (nm)
|
0.099
|
0.114
|
0.133
|
Physical state at room temp
|
gas
|
liquid
|
solid
|
Electronic configuration
|
|||
Boiling point (oC)
|
-34.5
|
58.6
|
184
|
Bond energy (KJ/mol)
|
242.5
|
191.5
|
150
|
Electron affinity(KJ/mol)
|
-364
|
-340
|
-297
|
Electronegativity
|
3
|
2.8
|
2.5
|
Solubility in water
|
soluble
|
soluble
|
Sparingly soluble
|
4
All are reactive non-metals and are not found in the elemental state in nature.
5
The colour intensity of Group 17 elements
increases down the group.
Chemical properties of Group 17
elements
Oxidizing properties
1. Halogens
are strong oxidizing agent. This is supported with the value of standard
reduction potential where
½ F2
(aq) + e- → F– (aq) Eo = + 2.87 V
½
Cl2 (aq) + e- → Cl– (aq) Eo = + 1.36 V
½
Br2 (aq) + e-→Br– (aq) Eo = + 1.07 V
½ I2
(aq) + e- → I– (aq) Eo = + 0.54 V
Quick
Check
1.
Among the halogen, which of the above is the strongest oxidizing agent ?
……………………………………………………………………………………………………………………………………
2.
List the halogens above in the descending order of oxidizing property
……………………………………………………………………………………………………………………………………
3. Write the electron configuration of
the following:
a)
Chlorine
b)
Bromine
c)
Iodine
4. Group 17 elements are coloured :
Chlorine
exist as _____________________ gas
Bromine
exist as _____________________ liquid
Iodine
exist as __________________gas and __________________ solid
5. As the proton number of the group
17 element increase the colour of the element become (darker/ lighter )
6. Q is an element in Group 17 which
is placed below Iodine in the Periodic Table.
What are the expected properties of Q at room condition ? [Cloned from STPM
2006]
Colour Physical state Oxidizing
power
A
Black Solid Weak
B Black Solid
Strong
C Violet Solid
Strong
D Violet Liquid
Weak
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