Group 7
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At room temperature, how does fluorine look?
Pale yellow gas (very reactive)
At room temperature how does chlorine look?
Green gas (reactive and poisonous in high conc)
At room temperature how does bromine look?
Red-brown liquid (gives off dense brown poisonous fumes)
At room temperature how does iodine look?
Shiny grey solid (sublimes to purple gas)
Describe the trend in the size of atoms down group 7.
Increases. Number of shells increases.
What is electronegativity?
The ability of an atom to attract electrons in a covalent bond towards itself.
What does electronegativity depend on?
The attraction between the nucleus and bonding electrons in the outer shell.
Describe the trend in electronegativity down group 7.
Decreases down the group.
Describe the trend in melting and boiling points down group 7.
Increases. Atomic radius increases. Number of electrons increases, VDW forces get stronger. Group 7 elements are simple covalent molecules with VDW forces. Strength of VDW forces increases down the group.
How do halogens form ions?
Gain an electron to become negative ion.
What kind of agents are halogens?
Oxidising agents.
Describe the trend in oxidising ability down group 7?
Decreases. Their ability to attract electrons decreases due to shielding and greater atomic radius.
What is a displacement reaction?
When an element is reduced and oxidised.
What kind of agents are halide ions?
Reducing agents.
Describe the trend in reducing power down group 7.
Increases. Electrons are easier to lose due to larger atomic radius and increased shielding.
What happens when solid sodium chloride reacts with sulfuric acid?
Steamy fumes of hydrogen chloride are seen. The product is sodium hydrogensulfate. NaCl (s) + H2SO4 (l) -> NaHSO4 (s) + HCl (g)
What is a disproportionation reaction?
The oxidation state of some atoms of the same element increase and others decrease.
What is formed when chlorine reacts with cold water in a reversible reaction?
Cl2 (g) + H2O (l) (reversible) HClO (aq) + HCl (aq)
What is chlorine used for?
Purifying water for drinking and swimming pools by killing bacteria. Chlorine can be toxic but the benefits of clean, treated water outweigh the risks.
What is HClO (chloric acid)?
An oxidising agent. Kills bacteria by oxidation. Bleach
What occurs when chlorine reacts with water in sunlight?
2Cl2 (g) + 2H2O (l) -> 4HCl (aq) + O2 (g) Chlorine is pale green HCl is colourless DONE IN THE PRESENCE UV LIGHT AS IT DECOMPOSES WATER TO PRODUCE O2 AND HCl
What is an alternative to using chlorine in swimming pools? Equations?
Solid Sodium/Calcium chlorate NaClO (s) + H2O (l) -> Na+ (aq) + OH- (aq) + HClO (aq)
What happens when chlorine reacts with cold, dilute sodium hydroxide?
Sodium chlorate (NaClO) is formed and NaCl and water.
What is sodium chlorate?
An oxidising agent Used in bleach