halogen group

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What elements are in the Halogen Family?

• Fluorine (F)
• Chlorine (Cl)
• Bromine (Br)
• Iodine (I)
• Astatine (At)

Where are the halogen elements located in the
periodic table?
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Group Halogen

• I. Physical properties of Group halogen elements.

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- The melting points and boiling points of the
halogens increase going down the group.
- The colours of the halogens get darker going
down the group.
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II. Structure of halogen molecule.
The Group VIIA elements are all non-metals. At
room temperature, they exist as diatomic
molecules, i.e. molecules made up of two
atoms F2, Cl2, Br2 and I2
There is a single covalent bond between the two
atoms in each molecule
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The electronic configurations of the Halogens.
Write the atom electron configuration of a
florine atom ( z9)?
How many electrons are in the outer shell of each
atom ?
Their atoms all have seven electrons in the outer
shell
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III. Reactions of Group halogen elements.
The halogen atoms need to gain just one more
electron to achieve the stable electronic
configuration of the noble gas atoms to the right
of them in the Periodic Table. Therefore they
react with metallic elements, with each of their
atoms gaining an electron from a metal atom to
become ions with a 1- charge.
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1. React with metals.
For example
When a halogen reacts with a metal atom, the
halogen atom gains one electron. Because of this,
the halogens are oxidising agents (electron
acceptors). In the process of oxidising another
substance they themselves are reduced.
Their oxidation number is reduced from 0 in the
element usually to -1 in the compound formed.
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In these experiments we find that the reactions
of ?uorine are more vigorous than chlorine.
Bromine reacts less vigorously than chlorine, and
iodine is less reactive than bromine
? The halogens get less reactive going down Group.
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This pattern in reactivity corresponds to the
trend in electronegativity going down the group,
shown in Table
Electronegativity values of the halogens.
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A ?uorine atom has the strongest pull on the pair
of electrons in a covalent bond, while an iodine
atom has the weakest attraction for electrons.
2. Reactions with hydrogen.
The halogens form hydrogen halides with hydrogen
gas.
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Determine the oxidation number change of halogen
elements ?
The oxidation number of halogens decreases from 0
to -1. ? Halogens are the oxidizing agent.
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3. DISPLACEMENT REACTIONS.
A more reactive halogen can displace a less
reactive halogen from a halide solution of the
less reactive halogen. Lets look at an example
When chlorine water, Cl2(aq), is added to a
solution of sodium bromide, containing Br-(aq)
ions, the solution changes to a yellowish brown
colour. The colour is caused by the presence of
dissolved bromine molecules, Br2(aq), as found in
bromine water. The displacement reaction that
takes place is
We say that chlorine has displaced bromine from
solution.
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This is summarised in the ionic equation for this
displacement reaction
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? Chlorine water is mixed with a solution of
potassium iodide in a test tube. a. Write a
balanced symbol equation, including state
symbols, for the reaction that occurs. b. Write
an ionic equation for this reaction.
Cl2(aq) 2KI(aq) ? 2KCl(aq) I2(aq)
Cl2(aq) 2I-(aq) ? 2Cl-(aq) I2(aq)
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Questions a. Which of these mixtures will result
in a chemical reaction? i. bromine solution and
sodium chloride solution 1 ii. iodine solution
and sodium bromide solution 1 iii. chlorine
solution and potassium bromide solution 1 iv.
bromine solution and sodium iodide solution
1 b. Write a balanced chemical equation for
each reaction that occurs in part a. 4 c. What
type of reaction occurs in part a? 1 d. What
trend do the reactions in part a show us? 1 e.
For one of the reactions that occurs in part a,
identify the substance oxidised and the substance
reduced. f. For one of the reactions that occurs
in part a, rewrite the equation as an ionic
equation.
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