GROUP 7

• what are group 7 known as


  Halogens
• are halogens diatomic molecules?


  Yes.
• structure of the halogens

  Simple molecular
• what ions do halogens form

  1- ions
• state of fluorine


  yellow gas
• state of chlorine


  green gas
• state of bromine


  brown/orange liquid
• state of iodine


  black/grey solid

  
  

  purple vapour
• atomic radius in group 7


  - Increases down the group:

  
  

  -Atomic number increases

  -Number of electrons in the atom increases (more shells)

  -Outer electron shells are increasingly further from the nucleus
• why does atomic size of a halogen affect the covalent bond between the diatomic molecules


  smaller atomic size = stronger covalent bonds due to being close to the nucleus
• what is electronegativity


  ability of an atom in a to attract electrons in a covalent bond to itself
• electronegativity down group 7


  - decreases down due to:

  
  

  -Atomic radius & shielding increases.

  -Distance of the outer electrons from positive nucleus increases.

  -Attraction between nucleus and bonding (shared) electrons decreases

  -also being shielded more

  - so ability to accept electron decreases
• which halogen attracts electron density towards itself in a covalent bond the weakest

  Iodine
• boiling point and melting point down the halogens

  -Increases down the group due to:

  
  

  -Halogen MOLECULES increase in size due to more electrons

  -Leading to greater Van der Waals forces between molecules

  -Increasing the energy needed to separate the molecules + therefore higher melting + boiling points
• reactivity of halogens


  -Decreases down the group due to:

  
  

  - The atomic radius increases

  - meaning the outer electrons are further away from the nucleus & more electron shielding.

  - further the outer shell electrons are from the positive nucleus, harder it is to attract another electron to complete the outer shell.
• ionisation energy down group 7

  -decreases

  
  

  - nucleus charge increases which strengthens

  - shielding increases which lowers

  - atomic radius increases which lowers
• general equation for halogen and metal

  halogen + metal -> metal halide
• what is the name of halogens when they get reduced of oxidised

  halides
• what is oxidation


  Loss of electrons, gain of oxygen, loss of H
• What is reduction


  gain of electrons, loss of oxygen, gain of H
• what do halogens act as

  oxidising agents
• do halogens get reduced or oxidised

  reduced - gains electrons
• reaction of bromide ions with chlorine


  - orange solution
• reaction of iodide ions with chlorine


  - brown solution
• reaction of iodide ions with bromine


  - brown solution
• oxidising agent power down group 7

  - decreases down the group due:

  
  

  -Atoms are larger / atomic radius increases

  -There is more shielding (due to extra electron shell)

  -Therefore decreased attraction between nucleus & outer shell electrons

  -Decrease in electron affinity (ability to accept electrons)

  - due to electronegativities
• State and explain the trend in oxidising ability of the elements down Group VII from chlorine to iodine. (4)

  1. oxidation power decreases

  2. more shells added

  3. atomic radius increase

  4. attraction for outer electrons decrease
• Explain how an aqueous solution of chlorine can be used to differentiate between separate aqueous solutions of sodium chloride, sodium bromide and sodium iodide.

  
  

  State what would be observed in each experiment and write equations for the reactions which occur. (9)

  1. NaCl + Cl2 no observable change

  2. NaBr + Cl2 orange/yellow solution formed

  3. of bromine

  4.NaI + Cl2 red/brown solution formed or black precipitate

  4. of iodine

  5. 2Br + Cl2 -> 2Cl + Br2

  6 2NaI + Cl2 à 2NaCl + I2
• Explain why iodine has a higher melting point than fluorine. (2)

  1. iodine is a bigger molecule/ it has more electrons

  
  

  2. there are more van Der walls between molecules
• reducing power down group 7

  increases down the group due:

  
  

  - Ionic radius of halide ion increases

  -Electron shielding increases

  -Outer electrons further from the nucleus so weaker attraction

  -Ions can lose an electron more easily

  - The larger the halide ion, the easier it is for it to donate electrons & therefore the more reactive it is
• observations and products of sulphuric acid + Sodium chloride

  - OBSERVATION: white fumes

  - PRODUCTS: HCl

  
  

  - acid base reaction
• observations and products of sulphuric acid + Sodium bromide

  - OBSERVATION: white fumes

  - PRODUCTS: HBr

  - acid base

  
  

  - OBSERVATION: Brown/orange fumes

  - PRODUCTS: Br2

  - redox

  
  

  - OBSERVATION: colourless gas with choking odour

  - PRODUCTS: SO2
• observations and products of sulphuric acid + Sodium iodide

  - OBSERVATION: white fumes

  - PRODUCTS: HI

  
  

  - OBSERVATION: purple fumes + black ppt

  - PRODUCTS: I2

  
  

  - OBSERVATION: colourless gas with a smell of bad eggs

  - PRODUCTS:H2S

  
  

  - OBSERVATION: colourless gas with choking odou

  - PRODUCTS: SO2

  
  

  - OBSERVATION: yellow ppt

  - PRODUCTS: S
• what is a halide

  metal + halogen
• SECRET HACK OF BALANCING REDOX EQUATIONS

  - the H+ and E- are on the same side

  - H2O on the lowest O to balance with the most O
• difference between reaction of H2SO4 with CL- and H2SO4 with BR-

  cl- is and acid base whilst br- is redox
• tests for halides


  - nitric acid

  - first add silver nitrate

  - dilute ammonia

  - conc ammonia
• silver nitrate + fluoride

  no reaction
• silver nitrate + chloride


  White precipitate
• silver nitrate + bromide


  cream ppt