Chemistry 3.2.3 Flashcards
What is the trend in atomic number down group 7?
Atomic number increases.
What is the trend in atomic radius down group 7?
Atomic radius increases. The electron is removed from a higher principle energy levels (more shielding) so the electron is further away from the nucleus.
What is the trend in boiling point down group 7?
Boiling point increases.
What is the trend in electronegativity Down group 7?
Electronegativity decreases as the size of the atom increases, so there are more principle energy levels (more shielding).
What is the appearance of F?
Pale yellow gas.
What is the appearance of Cl?
Pale green gas.
What is the appearance of Br?
Dark red/brown/orange liquid.
What is the appearance of I?
Dark purple/black solid.
Why is the boiling point of halogens weak?
Weak Van der Waals forces betweens molecules.
What is the trend in boiling point down group 7?
Increases as the size of the atom increases meaning more Van der Waals forces that need to be broken.
What does a halogen act as in a reaction?
Oxidising agent. Each halogen atom gains an electron from a halide ion, the halogen itself is reduced.
I2 + 2e- → 2I- or ½I2 + e- → X-
What is the trend in the power of halogens to act as oxidising agents down group 7?
Decreases as atomic radius increases. The effect of nuclear charge is reduced due to shielding.
How can the ability of a halogen to act as an oxidising agent be tested?
Add aqueous solutions of halogens to a colourless solution containing halide ions.
What happens when Cl2 reacts with Br-?
KBr and Cl2 forms a yellow/brown solution of Br2, so Cl2 oxidises Br-.
2KBr + Cl2 → 2KCl + Br2
2Br- + Cl2 → 2Cl- + Br2
What happens when Cl2 reacts with I-?
KI and Cl2 forms a black ppt of I2, so Cl2oxidises I-.
2KI + Cl2 → 2KCl + I2
2I- + Cl2 → 2Cl- + I2
