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AS LEVEL CHEMISTRY > 3.1.1 GROUP 7, THE HALOGENS > Flashcards

3.1.1 GROUP 7, THE HALOGENS Flashcards

1
Q

Describe and explain the trend in reactivity down group 7

A
  • Reactivity decreases down the
    group
  • Atomic radius increases due to
    increased number of shells
  • Greater shielding between
    positive nucleus and an outer
    electron, decreasing the
    electrostatic attraction felt.
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2
Q

What are the colours of the halogens? (vapours and solid)

A

Fluorine - colourless/pale yellow
Chlorine - yellow/green
Bromine - Brownish solution
Iodine - grey crystals/ purple vapour

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3
Q

What is the state of each halogen at room temperature?

A

Fluorine - gas
Chlorine - gas
Bromine - liquid
Iodine - solid
Astatine - solid

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4
Q

General properties of the halogens

A
  • Diatomic
  • Toxic
  • Volatile
  • Simple molecular structures
  • Very soluble (in water + other)
  • React with aluminium to produce
    WHITE TRIHALIDES
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5
Q

What is a commercial use of iodine?

A

As an antibacterial

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6
Q

What is electronegativity?

A

The tendency of an atom to attract a bonding pair of electrons in a covalent bond

(Measured with the Pauling scale)

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7
Q

Name the most and least electronegative elements

A

Most - Fluorine
Least - Francium and Caesium

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8
Q

What is the trend in electronegativity across the periodic table?

A

Electronegativity increases up groups and along periods

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9
Q

Describe and explain the trend in electronegativity down group 7

A
  • It decreases down the group
  • Larger atomic radius, more shells
  • Greater shielding
  • Weaker attraction between -
    positive nucleus and electron pair
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10
Q

Describe and explain the trend in melting and boiling point down group 7

A
  • Increases down the group
  • Larger molecules
  • Greater van der waals forces
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11
Q

Describe and explain the trend in first ionisation energy down group 7

A
  • Decreases down the group
  • Larger atomic radius, more shells
  • Greater shielding
  • Weaker attraction between outer
    electron and positive nucleus
  • More easily removed
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12
Q

What are the colours of the halogens in organic solvents?

A

**

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13
Q

Write the equations for halogens acting as oxidising agents, and halides acting as reducing agents

A

X2 + 2e- —— 2X-
^ Oxidising agent

2X- ——- X2 + 2e-
^Reducing agent

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14
Q

How does the oxidising ability of the halogens change down the group?

A

It decreases
Larger atomic radius, more shells
Greater shielding
Less electrostatic force felt between nucleus and another electron in a compound

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15
Q

Describe how the reducing ability of the halogens change down the group

A

Reducing ability increases
Greater shielding (Ar + shells)
Less attraction between outer electron and positive nucleus
Easier to lose an electron, as less energy is required to remove it

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16
Q

Why do redox reactions not happen when fluorine and chlorine react with concentrated sulfuric acid?

A

Fluorine and Chlorine are not strong enough oxidising agents

(instead undergo reaction with H2SO4 as a proton donor)

17
Q

Write a general form for the (acid) reaction between halide ions and concentrated sulfuric acid

A

X- + H2SO4 —— HX + NaHSO4

e.g. NaCl + H2SO4 – HCL + NaHSO4

18
Q

What are the properties of hydrogen halides?

A
  • Colourless gases at room
    temperature
  • Form steamy fumes in moist air
19
Q

What are the properties of hydrogen sulfide?

A
  • Colourless
  • Corrosive
  • Flammable
20
Q

What happens in the reaction between bromide ions and sulfuric acid?

A

Bromide ions reduce SO4 to SO2, and are oxidised to neutral Br2 molecules, producing water as well

H2SO4 + 2Br- + 2H+ – SO2 + Br2 + 2H2O

21
Q

State the charge on the hydrogen sulfate ion, and the oxidation numbers on the elements involved

A

HSO4 [-1]
H + 1
S - 2
O -2

22
Q

Describe what happens when concentrated sulfuric acid reacts with iodide ions

A
  • Sulfuric acid is reduced from S+6
    then to S+4, then to neutral sulfur.
  • Sulfur is then reduced to -2 in
    hydrogen sulfide, if there is
    enough iodine to reduce all the
    sulfur.
  • Water is also produced
  • Iodine acts as a reducing agent and is oxidised to I2 molecules
23
Q

What is the overall equation for when concentrated sulfuric acid reacts fully with iodide ions?

A

H2SO4 + 8I- + 8H+ – 4I2 + H2S + 4H2O

AS LEVEL CHEMISTRY (5 decks)

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