grp 17 elements
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what are some physical properties of halogens
• halogens are non-polar and have simple molecular structures. • halogens exist as diatomic molecules.
explain why bromine and iodine dissolve moderately in water.
weak interactions are formed between halogen and water molecules and hence insufficient amount of energy is released to overcome the strong intermolecular hydrogen bonds between water molecules for hydration to occur.
explain why halogens are soluble in organic solvents.
id-id interactions, of comparable strength to the original interactions in halogen and solvent, can be formed between halogen and organic solvent molecules, which releases sufficient energy to overcome id-id interactions in halogen and organic solvent, allowing halogen molecules to intermingle with organic solvent molecules and dissolve.
explain why does volatility of group 17 elements decrease down the group.
halogens are simple molecules with weak id-id interactions between halogen molecules. down the group, no. of electrons increase = greater momentary polarisation of the electron cloud = strength of id-id interactions increases = greater amt of energy required or overcome the stronger id-id inreraction = boiling point and melting point increase = volatility decreases down the group.
explain why does reactivity of halogens as oxidising agents decrease down the group. 2 explanations
based on electronegativity: - no. of filled principal quantum shell increases down the group and each successive element has its valence electrons located in a shell with a higher/larger principal quantum numbernn. - hence, valence electrons are increasingly further away form the nucleus and are less strongly attracted to the nucleus. - ability of atom to attract bonding electrons, and hence electronegativity, decreases down the group. - oxidising power of halogens decreases down the group. Based on standard electrode potential: - down the group, Enode becomes less positive - ability of halogens to be reduced decreases ability to oxidise other species decreases oxidising power of halogens decreases.
explain the displacement reaction of halogens.
halogens that are higher in group 17 are stronger oxidising agents and will oxidise aqueous halide ions that are lower in the group. halogen becomes halide ions, halide ions become halogens
explain how we can infer relative strength of oxidising agent from relative magnitude of change in OS.
if oxidising agent is stronger,it will gain electrons more readily and thus change in OS will be greater.
explain why thermal stability of hydrogen halides decreases down the group.
down the group, bond energy decreases as effectiveness of orbital overlap decreases(more diffused) . covalent bond strength decreases and hence thermal stability decreases. H-F bond canot be broken, H-Cl bond cannot decompose using Bunsen flame and H-Br bond can only be broken with strong heating.