group 7 Flashcards
What is group 7 also called?
The halogens
Group 7 elements are known as halogens.
What type of molecules do members of group 7 form?
Diatomic molecules
An example is F2.
What is the state of fluorine at room temperature and pressure?
Pale yellow gas
Fluorine is the lightest halogen.
What is the state of chlorine at room temperature and pressure?
Pale green gas
Chlorine is a diatomic molecule.
What is the state of bromine at room temperature and pressure?
Red brown liquid
Bromine is the only liquid non-metal at room temperature.
What is the state of iodine at room temperature and pressure?
Gray black solid
Iodine sublimates to form a violet gas.
What is the state of astatine?
Highly radioactive
Astatine has never been observed.
What trend is observed in the melting and boiling points of the halogens down group 7?
Both increase
This trend is due to intermolecular forces.
What type of lattice do halogens form when cooled?
Simple molecular lattice
This structure is held together by intermolecular forces.
What type of covalent bond exists between halogen atoms?
Strong covalent bond
Covalent bonds are not broken in the intermolecular interactions.
What are the intermolecular forces between halogen molecules called?
Van der waals
## Footnote
These forces are relatively weak.
What affects the strength of van der waals
The number of electrons
More electrons lead to stronger van der waals forces
How many electrons do iodine molecules have?
106 electrons
This is significantly more than fluorine molecules.
How many electrons do fluorine molecules have?
18 electrons
This contributes to weaker London forces compared to iodine.
What trend in electronegativity is observed in group 7?
Decreases down the group
This is due to increasing atomic radius and electron shielding.
What is electronegativity?
The ability of an atom to attract bonding electrons
It is a key concept in covalent bonding.
In hydrogen fluoride, which atom is more electronegative?
Fluorine atom
This creates a polar molecule.
What effect does bromine’s greater atomic radius have on its electronegativity compared to fluorine?
Reduces attraction to bonding electrons
The outer electrons are further from the nucleus.
What is the relationship between the number of electron shells and electronegativity down group 7?
More shells lead to less electronegativity
Inner shells shield bonding electrons from the nucleus.
What do halogens exist as?
Halogens exist as diatomic molecules, for example, Cl₂.
What happens when halogens react?
Halogens can remove an electron from another species.
What is the role of chlorine in a redox reaction?
Chlorine acts as an oxidizing agent by removing an electron from another species, which is oxidized.
What happens to the chlorine atom during the reaction?
The chlorine atom gains an electron and is reduced to form the chloride ion.
What is the electron configuration of the chloride ion?
The chloride ion has the electron configuration of the noble gas Argon.
How should halogens be represented in redox reactions?
Halogens should be shown as diatomic molecules in redox reactions.
Which halogen is the most reactive?
Fluorine is the most reactive and the most powerful oxidizing agent.
How does reactivity change down Group 7?
The reactivity of halogens decreases down Group 7 as they become less powerful oxidizing agents.
What is the electronic structure of fluorine?
Fluorine has an electronic structure that allows it to act as an oxidizing agent by removing an electron from another species.
What happens when bromine acts as an oxidizing agent?
Bromine gains one electron to form the bromide ion.
Why is bromine less reactive than fluorine?
Bromine has a greater atomic radius and more inner electron shells, leading to greater shielding and less attraction between the nucleus and outer electrons.
What is the effect of atomic radius on reactivity?
A greater atomic radius means outer electrons are further from the nucleus, making it harder to gain an electron.
What are halogens at the top of Group 7 compared to those near the bottom?
Halogens at the top of Group 7 are more powerful oxidizing agents than those near the bottom.
Which halogens should A-level students focus on?
A-level students should focus on chlorine, bromine, and iodine.
What is a displacement reaction involving halogens?
In a displacement reaction, a halogen in aqueous solution reacts with an aqueous solution of a metal halide.
What happens in the displacement reaction between chlorine and sodium bromide?
Chlorine displaces the bromide ion, forming bromine and sodium chloride.
Why does chlorine displace bromine in the reaction?
Chlorine is more reactive than bromine.
What is the oxidation state of chlorine and bromide ions at the start of the reaction?
Chlorine has an oxidation number of zero, and each bromide ion has an oxidation number of -1.
What happens to the oxidation states during the reaction?
Chlorine atoms are oxidizing bromide ions, and chlorine is reduced to chloride ions.
What are the final oxidation states of bromine and chloride ions?
Bromine has an oxidation number of zero, and chloride ions have an oxidation number of -1.
What is the significance of chlorine being a more powerful oxidizing agent than bromine?
This is why chlorine can displace bromine in the reaction.
What occurs in the displacement reaction between chlorine and sodium iodide?
Chlorine oxidizes iodide ions to iodine.
How does bromine compare to iodine as an oxidizing agent?
Bromine is a more powerful oxidizing agent than iodine.
What is the role of the metal ion in redox equations?
The metal ion is a spectator ion and does not take part in the redox reaction.
What color change occurs during a displacement reaction involving halogens?
A displacement reaction produces a color change due to the colored nature of halogens.
What issue arises with the colors of bromine and iodine in aqueous solution?
Both bromine and iodine can appear orange-brown in aqueous solution.
How can we better observe the colors of halogens formed in a reaction?
By adding a non-polar organic solvent like cyclohexane.
What colors do bromine and iodine appear in organic solvents?
In organic solvents, bromine appears orange, and iodine appears violet.
What color is chlorine solution at the start of the reaction with sodium bromide?
The chlorine solution is a pale green color.
What happens to the color of the upper cyclohexane layer after reacting chlorine with sodium bromide?
The upper layer turns orange due to dissolved bromine.
What color does iodine appear in aqueous solution and in cyclohexane?
Iodine appears brown in aqueous solution and violet in cyclohexane.
What is the color change when bromine reacts with sodium iodide?
It forms iodine, which appears brown in aqueous solution but violet in cyclohexane.
What is chlorine used for in drinking water?
Small amounts of chlorine are added to drinking water to kill harmful bacteria.
What are the products formed when chlorine reacts with water?
The products are chloric(I) acid and hydrochloric acid.
What is the role of chloric(I) acid?
Chloric(I) acid is a powerful oxidizing agent responsible for killing bacteria.
What type of reaction occurs when chlorine reacts with water?
This is a redox reaction.
What is the oxidation number of chlorine in hydrochloric acid?
In hydrochloric acid, the oxidation number of chlorine is -1.
What is the oxidation number of chlorine in chloric(I) acid?
In chloric(I) acid, the oxidation number of chlorine is +1.
What is a disproportionation reaction?
A disproportionation reaction is a redox reaction in which atoms of the same element are oxidized and reduced.
What diseases can chlorinated drinking water help prevent?
Chlorinated drinking water helps prevent waterborne bacterial diseases such as cholera.
What are the risks of using chlorine in drinking water?
Chlorine is a toxic gas and can react with naturally occurring hydrocarbons, potentially increasing cancer risk.
How soluble is chlorine in water?
Chlorine has a relatively low solubility in water.
What happens when chlorine reacts with cold, dilute aqueous sodium hydroxide?
A greater level of chlorine can react, producing sodium chloride and sodium chlorate(I).
What is the oxidation number of chlorine in sodium chloride?
In sodium chloride, the oxidation number of chlorine is -1.
What is the oxidation number of chlorine in sodium chlorate(I)?
In sodium chlorate(I), the oxidation number of chlorine is +1.
What is the use of the solution made from the reaction of chlorine and sodium hydroxide?
The solution is used as household bleach.
What do halogen atoms do in a reaction?
Halogen atoms can take an electron from another species, acting as oxidizing agents.
Which halogens are more powerful oxidizing agents?
Halogens at the top of Group 7 are more powerful oxidizing agents than those near the bottom.
What happens to a halogen atom when it accepts an electron?
The halogen atom is reduced, forming a halide ion.
What role do halide ions play in reactions?
Halide ions can donate their outer electron to another species, acting as reducing agents.
Which halide ions are more powerful reducing agents?
Halide ions at the bottom of Group 7 are more powerful reducing agents than those at the top.
Why is the fluoride ion a relatively weak reducing agent?
The fluoride ion has a small radius, making it difficult to lose an electron due to strong attraction to the nucleus.
Why is the bromide ion a more powerful reducing agent than the fluoride ion?
The bromide ion has a greater radius and more shielding, making it easier to lose an electron.
What is observed when Group 1 halides react with concentrated sulfuric acid?
Different products are formed as the reducing power of the halides increases.
What products are formed when sodium chloride reacts with concentrated sulfuric acid?
Sodium hydrogen sulfate (a white solid) and hydrogen chloride gas (which forms white fumes in moist air).
What type of reaction occurs with sodium chloride and concentrated sulfuric acid?
This is not a redox reaction; the chloride ion is a weak reducing agent.
What products are formed when sodium bromide reacts with concentrated sulfuric acid?
Sodium hydrogen sulfate, hydrogen bromide gas, sulfur dioxide gas, and bromine (orange).
What changes occur in oxidation numbers during the reaction of sodium bromide with sulfuric acid?
Sulfur is reduced from +6 to +4, and bromide is oxidized from -1 to 0.
What products are formed when sodium iodide reacts with concentrated sulfuric acid?
Sodium hydrogen sulfate and hydrogen iodide, along with several products due to iodide’s reducing power.
What can iodide reduce sulfur to in sulfuric acid?
Sulfur can be reduced to +4 (sulfur dioxide), 0 (elemental sulfur, S₈), or -2 (hydrogen sulfide gas).
What is the smell of hydrogen sulfide gas?
Hydrogen sulfide gas has a rotten egg smell.
What is the equation for the formation of hydrogen sulfide?
The sulfur is reduced from +6 to -2, and iodide is oxidized from -1 to 0.
