Groups in the Periodic Table

• What is the trend in density down group 0?

  Density increases down the group.

  Helium is the least dense and radon is the most dense
• What is the trend in boiling points down group 0?

  Boiling point increases down group 0 because the relative atomic mass increases so there are more intermolecular forces between atoms
• Why is argon used for welding?

  • It provides an inert welding atmosphere

  • Argon is more dense than air so keeps air away from the metal
• Why is argon used to fill electric light bulbs?

  It is very chemically inert so will not react when the light bulb gets hot. It is non-flammable
• What properties of helium makes it suitable for use in balloons?

  It is less dense than air and does not burn
• Why are the noble gases chemically inert?

  • They have full outer electron shells

  • This is a very stable electron configuration and means the elements are very unreactive
• What does chemically inert mean?

  Not chemically active
• How many electrons do the noble gases have in their outer shell?

  • 0

  • They have no incomplete shells of electrons
• What name is used to describe the elements in group 0 of the periodic table?

  Noble gases
• Bromine reacts with potassium iodide. What is reduced and what is oxidised?

  • Bromine is reduced to bromide ions

  • lodide ions are oxidised to iodine
• Are halogen displacement reactions redox reactions? Explain your answer

  • Yes

  • The halide ion is oxidised (loses an electron) to form a halogen atom

  • The halogen is reduced (gains an electron) to form a halide ion
• What is a redox reaction?

  A reaction where oxidation and reduction take place at the same time
• What would you observe when chlorine is added to potassium bromide?

  Colour change from colourless to orange
• What colours are solutions of chlorine, bromine and iodine?


  • Chlorine water - colourless

  • Bromine water - orange

  • Iodine solution - brown
• Why does reactivity decrease down group 7?

  • As you go down group 7, the outer shell is further from the nucleus and electron shielding increases

  • Attraction between the nucleus and outer electrons decreases so it is harder for the atom to gain an electron meaning reactivity decreases
• Which halogens would you expect astatine to be able to displace?

  • None of them

  • It is at the bottom of group 7 so has the lowest reactivity
• Write the word equation for the reaction between bromine and calcium chloride

  No reaction will occur because bromine is less reactive than chlorine so chlorine won't be displaced
• Write the word equation for the reaction between chlorine and potassium bromide

  Chlorine + potassium bromide → potassium chloride + bromine
• Why can iodine not displace chlorine or bromine from an aqueous ionic solution?

  • Because reactivity decreases down the group and iodine is below chlorine and bromine group 7

  • Displacement will only occur if iodine is more reactive than the halogen in the ionic compound
• Which halogens can't be displaced from an aqueous ionic solution by bromine?

  • Bromine can't displace any halogens above it in group 7

  • These are chlorine and fluorine
• Which halogens can chlorine displace from an aqueous ionic solution?

  • Chlorine can displace any halogens below it in group 7

  • It will displace iodine and bromine
• When does a halogen displacement reaction occur?

  When a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide
• Predict the product of the reaction between hydrogen and fluorine

  Hydrogen fluoride
• What is formed when a hydrogen halide dissolves in water?

  An acidic solution. Hydrogen ions dissociate, making the solution acidic
• Chlorine reacts with hydrogen in the presence of sunlight but bromine requires a flame. Why?

  Reactivity decreases down the group so bromine requires more energy for the reaction to occur
• What is formed when hydrogen reacts with a halogen?

  Hydrogen halides
• Describe the trend in reactivity of the halogens. How does this affect the rate of reaction?

  • Reactivity decreases down group 7

  • Rate of reaction decreases down group 7
• Write a word equation for the reaction between iodine and potassium

  • lodine + potassium → Potassium iodide

  (Remember - the ion of a halogen ends with -ide)
• Predict the product of the reaction between magnesium and fluorine

  Magnesium fluoride
• What is produced when a halogen reacts with a metal?

  Metal halide salt
• What charge does a halide ion carry? Why?

  • -1

  • They gain one electron to have a stable electron configuration
• Halogens are diatomic. What does this mean?

  They form molecules consisting of 2 atoms
• What is the chemical test for chlorine?

  • Damp litmus paper placed into a test tube of gas

  • If chlorine is present, the litmus paper will turn red then white due to the bleaching effect of chlorine
• Why does melting and boiling point increase down Group 7?

  The molecules get bigger down the group so there are more intermolecular forces to overcome during melting / boiling so more energy is required
• What state would you expect the halogens fluorine and astatine to be at room temperature?

  • Fluorine is above chlorine so should have a boiling point lower than chlorine. This means it would be a gas at room temperature

  • Astatine is below iodine in group 7 so should have a higher melting point than iodine. Therefore you can predict that it would be a solid at room temperature
• Why are the halogens at different states at room temperature? What is the trend down the group?

  • At room temperature, chlorine is gaseous, bromine is liquid and iodine is solid because they have different melting and boiling points

  • As you go down the group, melting and boiling point increases
• What is the colour and state of iodine at room temperature?

  Black solid
• What is the colour and state of bromine at room temperature?

  Red-brown liquid
• What is the colour and state of chlorine at room temperature?

  Pale green gas
• What group are the halogens in? Why?

  Group 7 because they have 7 outer shell electrons