Halogens & noble gases

• NOBLE GASES

  GROUP 0 elements, which has complete outer electron shells, this makes them unreactive and COLOURLESS at room temperature.

  • Reactivity does not change down the group.
  • They are NON-FLAMMABLE (doesn't catch fire), a significant safety feature in applications.

  
• Noble Gases

  Doesn't form molecules and exist as SINGLE MONATOMIC ATOMS (just one atom), since their outer shell is full, so no need to lose or gain electrons.

  
• monatomic:

  • one atom

  diatomic:

  • two atoms
• Noble gases have boiling points that increase down the group, with increasing relative atomic mass:

  • due to the increasing number of sub-atomic particles
  • which increases intermolecular forces, so it needs more energy to break the forces that change state from liquid to gas.
• intermolecular

  the attractive forces between molecules of a substance.
• what type of particles are in a sample of neon?

  atoms
• In reactions, metals give away outer shell electrons to non-metals, until both has a full outer shell.
• HALOGENS 

  the NON-METALS found in GROUP 7, all halogens have 7 electrons in the outer shell making them react in similar ways.

  • these are diatomic molecules.

  
• properties of halogens:

  A) increases

  B) darker

  C) decreases

  
• Explain the trend in reactivity of the halogens:

  • It has 7 outer electrons, so it needs to gain an electron to become stabled.
  • halogens further down the group are less reactive because they have more shells, so less attractive force on the electrons , this makes an electron less easily gained.

  
• going down group 7, the melting and boiling points increase, because the size of the molecules increases so the intermolecular forces increase, meaning MORE ENERGY is needed to separate the molecules.
• The reactivity decreases down group 7, because chlorine has 2 reactions and bromine has one reaction.

  
• Predict what you would observe when fluorine gas reacts with iron:

  • burns very vigorously
  • explodes
  • burns violently
  • brighter glow
  • flame
• Here's a list with all the possible DISPLACEMENT reactions:

  A) X

  B) X

  C) X

  D) KCl + Br2

  E) X

  F) X

  G) KCl + I2

  H) KBr + I2

  I) X

  
• Explain why chlorine is more reactive than bromine

  chlorine is a smaller atom and has the greater attraction between the nucleus and the outer shell, therefore chlorine can gain an electron more easily.
• Halogens react with NON-METALS


  They form SIMPLE MOLECULAR compounds (contains only a few atoms) with COVALENT BONDS (sharing of electrons).

  • Word Equation:
  • Hydrogen + Chlorine -> Hydrogen Chloride
  • Symbol Equation:
  • H2(g) + Cl2(g) -> 2HCl(g)
• HALOGENS undergo DISPLACEMENT REACTIONS


  A MORE REACTIVE halogen REPLACES a LESS REACTIVE halogen in a compound.

  For e.g. Chlorine can displace Bromine in Potassium Bromide:

  • Word Equation:
  • Potassium + Chlorine -> Potassium Chloride + Bromine
  • Symbol Equation:
  • 2KBr(aq) + Cl2(g) -> 2KCl(aq) + Br2(aq)
• HALOGENS undergo DISPLACEMENT REACTIONS


  If the halogen is LESS REACTIVE, the displacement reaction will NOT occur

  • Word Equation:
  • Potassium Chloride + Bromine -> No reaction
  • Symbol Equation:
  • 2KCl(aq) + Br2(l) -> no reaction
• Halogens react with METALS


  They form IONIC compounds with ionic bonds.

  For example:

  • Word Equation:
  • Sodium + Chlorine -> Sodium Chloride
  • Symbol Equation:
  • 2Na(s) + Cl2(g) -> 2NaCl(s)
• Word Equation:

  • Iron + Bromine -> Iron Bromide

  Symbol Equation:

  • 2Fe + 3Br2 -> 2FeBr3
• Chlorine, Iodine and Astatine are in group 7 of the modern periodic table.

  • Astatine (At) is below Iodine in Group 7.

  Formula of an astatine molecule:

  • At2

  State at room temperature:

  • Solid