Periodicity Flashcards

• Ammonium Ions Test

  Aqueous ammonium ions and Aqueous hydroxide ions react to form ammonia gas. The mixture is then warmed and tested with damp red litmus paper and should turn blue since its an alkaline
• Mixture of Ions?

  Carry out test in the same order

  
  

  Carbonate - Continue adding nitric acid till effervescence stops

  
  

  Sulphate - Add excess of Barium Nitrate, any ions left will form a ppt of barium sulphate then filter solution to remove the barium sulphate

  
  

  Halide - Add NH3 to confirm
• What is the sequence of testing?

  Carbonate - The other two don't produce bubbles with nitric acid

  Sulphate - Barium carbonate is also white and insoluble, so you should rule out the possibility of a carbonate earlier on

  Halides
• Sulfate Test

  Barium Ions are added to the solution

  Barium Sulphate is formed

  Its a white ppt and is insoluble in water
• Carbonate Test

  Add nitric acid to the solution

  If you see effervescence it could be a carbonate

  Bubble the gas through limewater

  If it turns cloudy/milky as a white ppt has formed a carbonate ion is present
• Testing for Halide Ions

  Aqueous Halides react with Aqeuous Silver Ions to Form Precipitates of Silver Halides

  
  

  Ag+ + X- --> AgX

  
  

  Chlorine - White

  Bromine - Cream

  Iodine - Yellow

  
  

  Add aqueous ammonia to test solubility since colours can be difficult to tell apart

  
  

  Chlorine - Soluble in dilute NH3

  Bromine - Soluble in conc. NH3

  Iodine - Insoluble in conc. NH3
• Benefits and Risks of Using Chlorine

  Chlorine is used to kill bacteria, however in large quantities it can be toxic as its a respiratory irritant
• Reaction of Chlorine and Cold Dilute Aqueous NaOH

  NaClO is formed as well as NaCl and H2O
• Reaction of Chlorine and Water

  Products are Chloric Acid (HClO)and Hydrochloric Acid (HCl)

  Chlorine is used in water purification as a disinfectant

  Chloric Acid is also a weak bleach
• What is a disproportionation reaction?

  In a redox reaction the same element is both oxidised and reduced
• Trends in Reactivity of Halogens

  Atom Radius increases

  Shielding increases because there are more inner shells

  Less Nuclear Attraction

  Therfore Reactivity Decreases
• Chlorine and Bromine Ions

  Chlorine is reduced and Bromine is oxidised
• Iodine Solution in Cyclohexane changes colour to


  Violet
• Bromine Solution in Cyclohexane changes colour to

  Orange
• To distinguish the colours of the halogens in water, what is added?

  An organic non-polar solvent is used eg. cyclohexane
• Iodine in Water changes colour to

  Brown
• Bromine in Water changes colour to

  Orange
• Chlorine in Water changes colour to

  Pale Green
• Halogen-Halide Displacement Reactions


  Reactivity of Halogens decrease down the group

  The tested halogen solution is added to the aqueous solutions containing the halide ions of the other two and if it displaces it there is a colour change
• Redox Reactions of Halogens

  Each halogen atom is reduced

  Cl2 + 2e- --> 2Cl-

  Halogens are Oxidising Agents
• Trends in Boiling Points of Halogens

  BP increases down the group

  More electrons

  Stronger London Forces

  More energy required to break the intermolecular forces

  Chlorine is a gas and Iodine is a solid at RTP
• Group 2 Compounds in Medicine

  Used as Antacids

  Neutralisation reaction takes place between the acid and base
• Group 2 Compounds in Agriculture

  Calcium Hydroxide is added to increase the pH of acidic soils - it neutralises the acid in the soil forming water
• Solubility of Group 2 Hydroxides

  Solubility increases down the group

  Solutions have more OH- ions and are more alkaline/pH increases
• Group 2 Oxides and Water

  Release OH- ions and form the alkaline solutions of metal hydroxides

  Slightly soluble in water

  The above further reacts to form the metal hydroxide precipitate
• Group 2 Trends in Reactivity and IE

  Reactivity increases down the group because the atom requires the input of two ionisation energies
• Group 2 Metals Reacting with Dilute Acids

  Form a Salt and Hydrogen Gas

  The metal is oxidised and the hydrogen is reduced
• Group 2 Metals Reacting with Water

  Form and Alkaline Hydroxide and Hydrogen Gas

  GF: M(OH)2

  Down the group the reactivity increases and becomes more vigorous
• Group 2 Metals Reacting with Oxygen

  Form a Metal Oxide

  Made of M2+ and O2+ ions

  The metal is oxidised and the oxygen is reduced
• Why are Group 2 Metals Reducing Agents?

  In redox reactions, each metal atom is oxidised losing two electrons. Another species will gain these two electrons and that species will be reduced. Therefore Group 2 Metals are reducing agents
• Trends of Melting Points in The Periodic Table

  Melting point increases from Group 1 to 14

  Sharp decrease between Group 14 and 15 (due to the change from giant to simple molecular structures)

  Low melting points for Groups 15 to 18
• Properties of Non-Metals: Electrical Conductivity


  All are non-conductors apart from Graphene and Graphite. These can conduct electricity because each carbon atom has a free delocalised electron that is mobile and can carry the charge through the structure
• Properties of Non-Metals: Solubility

  Insoluble in all solvents

  The covalent bonds are far too strong to be broken by interacting with solvents
• Properties of Non-Metals: Melting and Boiling Points

  Have high melting and boiling points because covalent bonds require lots of energy to break them
• The structure of atoms bonded by strong covalents bonds are known as

  Giant Covalent Lattice
• Solubility of Metals

  Metals are not soluble however, there may be some interaction between polar solvents and the charges in the lattice - this would lead to a reaction rather than it dissolving
• Properties of Metals: Melting and Boiling Points

  Melting point of metals depends on the strength of the metallic bonds. High temperatures are needed to overcome the strong electrostatic attraction, therefore have high melting and boiling points
• Properties of Metals: Electrical Conductivity

  In solid and liquid states delocalised electrons are mobile, so they can move through the structure and carry the charge
• Metallic Bonding


  Strong electrostatic attraction between cations (metal ions, these are fixed giving structure) and anions (delocalised electrons, are mobile )

  Held together in a Giant Metallic Lattice
• Comparing Nitrogen and Oxygen


  The fall marks the pairing of electrons in the 2p subshell.

  In oxygen the paired electrons repel one another making it easier to remove the electron therefore the ionisation energy is less than nitrogen