Group 7- The Halogens
- Created by: LegendofZelda
- Created on: 28-03-18 11:34
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- Group 7 - The Halogens
- Physical properties
- gases become darker and denser as you descend group 7
- Have a familiar pool smell
- Melting and boiling points increase going down group
- Atoms become larger as you descend-have lager vdw forces
- Need more energy to break the larger vdw forced
- Chlorine more volatile than iodine (solid)
- Atomic size increases going down group
- Extra shell is added for each element- has one more outer shell than the one above
- E.g. fluorine has 3p as its outer shell. Chlorine, which is below flourine, has 4p outer shell
- Extra shell is added for each element- has one more outer shell than the one above
- Electronegativity decreases down group
- The power of an atom to attract the electron density of a covalent bond to itself
- Valence electrons get further away from nucleus as you go down group and shielding is increased
- Decreases electrostatic attraction of outer electrons to nucleus valence electrons have less attraction to nucleus
- It becomes harder to gain electrons or pull them closer due to the lack of attraction descending the group
- It becomes harder to gain electrons or pull them closer due to the lack of attraction descending the group
- Decreases electrostatic attraction of outer electrons to nucleus valence electrons have less attraction to nucleus
- Displacement reactions
- Halogens reacting in a solution with metal halides- the halide in the compound will be dispaced by more reactive halogen
- E.g. iodine could not displace chlorine but fluorine could
- Reactivity of halogens decrease down the group
- Cl2 + 2NaBr ---> Br2 + NaCl
- In aqueous solution
- Halogens reacting in a solution with metal halides- the halide in the compound will be dispaced by more reactive halogen
- Oxidising Ability of halogens
- Decreases down group
- Halogens are oxidising agets- lose electrons to become -ve ions with a charge of -1
- Reactions of halide ions
- Sodium halides and sulfuric acid
- Sdoum chloride
- Fumes of HCl and solid sodium hyrdogensulfate are produced
- NOT A REDOX REACTION as chlorine is too weak a reducing agent. It is an acid-base reaction
- Sodium Bromide
- Fumes of hydrogen bromide, brown fumes of bromine and colourless SO2
- FIRST REACTION IS ACID- BASE SECOND IS REDOX
- Fumes of hydrogen bromide, brown fumes of bromine and colourless SO2
- Sodium Iodide
- Fumes of hydrogen iodide, black solid iodine and bad smell of hydrogen sulfide gas
- NaI + H2SO4 --> NaHSO4 + HI
- 8I- + H2SO4 --> H2S + 4H2O + 4I2
- Redox reaction
- Acid-base reaction
- 8I- + H2SO4 --> H2S + 4H2O + 4I2
- Sdoum chloride
- Testing for halide ions
- Add dilute nitric acid to halide solution to remove impurities e.g. CO32-
- Then silver nitrate is added-halide ppt forms
- White ppt=chloride ions Cream ppt=bromide ions Yellow ppt=iodide ions
- Chloride ions soluble in dilute NH3 but bromide ions only dissolve in conc. NH3
- After pt is formed, ammonia can be added to distinguish between similar colours
- White ppt=chloride ions Cream ppt=bromide ions Yellow ppt=iodide ions
- Sodium halides and sulfuric acid
- Physical properties
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