Group 17

Question 1

Explain the trend of volatility of Group 17 elements down the group.

Answer 1

Down the group, number of electrons increases. Hence electron cloud becomes more polarisable and stronger idid. Thus more energy is required to overcome stronger idid. Thus volatility decreases down the group.

Question 2

Explain the reactivity of elements of group 17 as oxidising agents

Answer 2

• Number of protons increases hence nuclear charge increases
• Number of electron shells increases hence shielding effect increases
• Effective nuclear charge increases and valence electrons are less strongly bonded to nucleus
• Lesser energy is given out, 1st EA less exothermic
• E becomes less positive
• Oxidising power and reactivity decreases

Question 3

Write down the reactions of Cl2, Br2, I2 with thiosulfate S2O3^2-.

Answer 3

4Cl2 + (S2O3 2-) –> 8Cl- + 2(SO4 2-) + 10H+
4Br2+ (S2O3 2-) –> 8Br- + 2(SO4 2-) + 10H+
I2 + 2(S2O3 2-) –> 2I- + (S4O6 2-)

Question 4

Explain the trend in thermal stability of group 17 hydrides

Answer 4

Down the group, atomic radius increases. The valence orbital is larger and more diffuse. There is less effective orbital overlap between 1s orbital of hydrogen and the valence p orbital of halogen. H-X bond energy decreases and the hydride is less thermally stable.

Question 5

Explain the trend of acidity of group 17 hydrides down the group

Answer 5

Down the group, atomic radius increases. The valence orbital is larger and more diffuse. There is less effective orbital overlap between 1s orbital of hydrogen and the valence p orbital of halogen. H-X bond energy decreases and less energy is required to form H+, acidity increases.