Trends and Reactions of Group 7 Elements (Halogens)

These flashcards cover key concepts related to the trends and reactions of Group 7 elements (halogens) in chemistry, including their properties, reactions, and behavior in displacement and redox reactions.

Halogens

The Group 7 elements known for their distinct properties and uses.

Volatility

A measure of how easily a substance can evaporate; low boiling points indicate high volatility.

Diatomic molecules

Molecules consisting of two atoms, which halogens exist as at room temperature.

London dispersion forces

Weak intermolecular forces arising from induced dipoles due to electron movement.

Electronegativity

The ability of an atom to attract electrons in a covalent bond.

Oxidising agent

A substance that gains electrons in a chemical reaction, causing another substance to be oxidised.

Displacement reaction

A reaction where a more reactive halogen displaces a less reactive halogen from its compounds.

Redox reaction

A reaction involving both reduction and oxidation processes.

Fluorine

The most volatile halogen.

Iodine

The least volatile halogen, with the highest melting and boiling points.

Halide ions

The ions formed when halogens gain one electron.

AgNO3 (silver nitrate) test

A test used to identify halide ions by forming a precipitate.

Chlorine's use in water treatment

Chlorine is used to disinfect and purify drinking water.

Sodium and chlorine reaction

Produces sodium chloride as Na(s) + Cl(g) → 2NaCl(s).

Bromine's appearance in reactions

Reacts slowly in heat, producing reddish-brown bromine gas.

Iodine's appearance in reactions

Forms purple vapor when heated.

Hydrochloric acid formation

Produced when hydrogen reacts with chlorine: Cl(g) + H2(g) → 2HCl(g).

Chlorine disproportionation

A reaction where chlorine is simultaneously oxidised and reduced.

Halide ion solubility in ammonia

Chloride dissolves in both dilute and concentrated ammonia; bromide dissolves in concentrated ammonia, iodide does not.

Chloric(I) acid (HClO)

Chlorine compound formed during chlorination of water.

Reduced form of iodine

Oxidised from iodide ions to molecular iodine in reactions.

Displacement observation

Chlorine displacing bromine results in a yellow-orange solution.

Electronegativity trend in halogens

Electronegativity decreases as you move down the group.

Oxidation state change in halogens

Halogens change oxidation state during reactions: 0 to -1 when gaining an electron.

Sulfur dioxide production

Result of hydrogen bromide reacting with sulfuric acid : 2HBr(g) + H2SO4(l) → Br2(g) + SO2(g) + 2H2O(l).

Attraction of electrons trend

Decreases down the group as atomic size increases.

Molecular structure of halogens

Halogens are simple molecular structures made up of diatomic molecules.

Hydrogen iodide properties

Hydrogen iodide decomposes, forming various products when reacting with sulfuric acid.

Visual changes in halide reactions

Color changes (such as purple for iodine) indicate displacement and redox reactions.

Laboratory safety with toxic gases

Use fume cupboards when working with concentrated sulfuric acid and halide ions.

Hydrogen halide production

Produced when halogens react with hydrogen.

Iodide ion tests with AgNO3

Forms a precipitate with silver nitrate confirming the presence of iodide.

Relative reactivity of halogens

Decreases down Group 7 (F > Cl > Br > I).

Chlorine's ability to oxidise

Chlorine can oxidise metals and other non-metals.

Bromide ion behavior

More reactive than iodide but less than chlorine.

Thermal stability of hydrogen halides

Decreases down the group, affecting the reaction outcomes.

Sulfuric acid's role in halide reactions

Concentrated sulfuric acid acts as an oxidising agent in halide reactions.

Precipitate dissolving behavior

Dissolves differently depending on the halide ion in reaction with ammonia.

Group 7 elements color trend

Colors darken as you move down the group.

Concentration effect on iodide's reaction

Hydrogen iodide can be oxidized by sulfuric acid resulting in a range of products.

Hydrogen bromide properties

Experiences oxidation and decomposes in reactions, releasing toxic gases.

Chlorine in water purification

Chlorine removed harmful bacteria, making water safe to drink.

Increasing atomic size in halogens

Results in weaker nuclear attraction, decreasing oxidising ability.

Electrochemical series

Halogens can be ranked based on their ability to oxidise other substances.

Group 7 vs. metals

Halogens act as non-metals and are generally much more electronegative than metals.

Ionic compounds formed by halogens

Halogens react with metals to form salts.

Oxidation state behavior in redox

Identifying the changes in oxidation states helps visualize redox reactions.

Fluorine's unique properties

Fluorine is highly reactive and can form stable compounds easily.

Spectator ions in reactions

Components that do not change in oxidation state during reactions.

Reducing agents strength

Strength increases down the group due to size and electron affinity.

Hydrogen gas in halides

A byproduct of reactions with halides and metals.

Chlorine reaction with metals

Chlorine can react vigorously with metals, demonstrating its oxidizing properties.

Silver iodide characteristics

Silver iodide does not dissolve in ammonia, unlike silver chloride and bromide.

Silver halide precipitates

Color and solubility variations help identify different halide ions.

Cl2 in reaction analysis

Always used to test for the presence of certain halide ions due to its reactivity.

Hydraulic acid properties

Produced when a halogen interacts with hydrogen, forming an acid.

Halo-acids behavior in solution

Dissociation in water forms strong acids like hydrochloric acid.