Chapter 9 - Group 2 and the Halogens Flashcards
What is the charge of a group 2 ion?
+2
What do the electron configurations in group 2 end in?
s2
Atomic radius ……… down group 2.
Increases
Reactivity ……… down group 2.
Increases
First ionisation energy ……… down group 2.
Decreases
What is formed when group 2 elements react with water?
Metal hydroxides and hydrogen (except magnesium which forms an oxide)
What state are group 2 oxides at room temperature?
White solids
What group number are the halogens?
7 (or 17)
What is the appearance of Fluorine at room temperature?
Pale yellow gas
What is the appearance of Chlorine at room temperature?
Pale green gas
What is the appearance of Bromine at room temperature?
Brown/orange liquid
What is the appearance of Iodine at room temperature?
Grey solid
Boiling points …….. down group 7.
Increase
Stronger induced dipole-dipole (London) forces require more energy to be broken.
Electronegativity ……… down group 7.
Decreases
Atomic radius and shielding increases.
During a displacement reaction, which organic solvent is added to help identify the halogen?
Hexane
Reactivity ……… down group 7.
Decreases
What happens when a halogen is reacted with a halide ion?
If the halogen is more reactive than the halide ion (lower on the periodic table), it will displace the halide ion. (e.g. Cl2 + 2Br = 2Cl- + Br2 as chlorine is more reactive than bromine)
When reacted with silver nitrate, what colours are the precipitates of chloride, bromide, and iodide ions?
Chloride - white precipitate
Bromide - cream precipitate
Iodide - yellow precipitate
Why is nitric acid added to precipitation reactions before the silver nitrate?
Nitric acid will react with any anions other than the halides, so that they will not react with the silver nitrate.
How can the present halide in a precipitation reaction be identified using ammonia?
Chloride - precipitate dissolves in dilute NH3
Bromide - precipitate dissolves in concentrated NH3
Iodide - precipitate insoluble in concentrated NH3
What is a disproportionation reaction?
Where one element is both oxidised and reduced simultaneously.
What are the advantages of adding chlorine to drinking water?
- Destroys disease-causing microorganisms
- Reduces bacteria build up
- Reduces growth of algae in water
What are the disadvantages of adding chlorine to drinking water?
- Chlorine gas is toxic and irritates the respiratory system
- Liquid chlorine can cause severe chemical burns to the skin
- Can react with organic compounds in the water to produce chloroalkanes, which have been linked to causing cancer.
What is the test for ammonium ions?
Add NaOH, and shake. Hold damp red litmus paper over, and will turn blue if ammonium gas is produced.
