Halogens and Halides

Halogens and Halides

• Halogens include Fluorine, Chlorine, Bromine, Iodine, and Astatine.
• Halides are the ions or compounds that form, when halogens react.
• Examples of halides are fluoride, chloride, bromide, and iodide.

Physical vs Chemical Properties

• A physical property can be observed without altering the substance.
• Examples of physical properties include color, state.
• A chemical property involves changing the substance's identity.
• Examples of chemical properties include reactivity with another substance.

Trends in Halogen Properties

• As you go down the halogen group, they become darker in color.
• As you go down the halogen group, they go from gases to solids.
• Observed trends, like increasing boiling point/decreasing reactivity, can estimate properties of halogens.

Colors of Halogens

• Fluorine is pale yellow.
• Chlorine is green.
• Bromine is red-brown.
• Iodine is dark grey as a solid and purple as a gas.

Aqueous Solutions of Halogens

• Chlorine is pale green in aqueous solution.
• Bromine is orange in aqueous solution.
• Iodine is brown in aqueous solution.

Halogen Displacement Reactions

• In Group 7, more reactive halogen displaces a less reactive halogen from its halide compound.
• Reactivity decreases as you go down Group 7.
• An experiment involves adding a halogen solution to a halide solution and observing for displacement.

Gases in the Atmosphere

• The main gases in the air are Nitrogen, Oxygen, Argon, and Carbon Dioxide.
• Nitrogen accounts for approximately 78% of the air by volume.
• Oxygen accounts for approximately 21% of the air by volume.
• Argon accounts for approximately ~1% of the air by volume.
• Carbon Dioxide accounts for approximately ~0.04% of the air by volume.
• Reacting air with iron or phosphorus and measuring the volume decrease can determine oxygen percentage.

Determining Percentage of Oxygen in Air

• Experimental setup uses a gas syringe or bell jar, tracking how oxygen is consumed in a reaction.
• Metals like iron or non-metals like phosphorus remove oxygen from air in an experiment.

Combustion

• Combustion is a chemical reaction where a substance reacts with oxygen, producing heat and light.
• Magnesium combusts with a bright white flame and produces white ash.
• Hydrogen combusts with a squeaky pop and produces water vapor.
• Sulfur combusts with a blue flame and produces sulfur dioxide gas.
• Magnesium + Oxygen yields Magnesium oxide.
• Hydrogen + Oxygen yields Water.
• Sulfur + Oxygen yields Sulfur dioxide.
• 2Mg + O2 yields 2MgO.
• 2H2 + O2 yields 2H2O.
• S + O2 yields SO2.

Thermal Decomposition

• Thermal decomposition is breaking down a compound using heat.
• Copper carbonate decomposes into Copper oxide + Carbon dioxide.
• CUCO3 decomposes into CuO + CO2.

Climate Change and Rusting

• CO2 traps heat in the Earth's atmosphere.
• Rusting requires both water and oxygen.
• Rusting is specific to iron, while corrosion is a general term for metals wearing away.
• Rusting can be prevented by painting, oiling, or coating with plastic.
• Galvanising is coating iron with zinc to prevent rust.
• Sacrificial protection involves attaching a more reactive metal, so it corrodes instead of the iron.