groups in the periodic table

• how are elements arranged in the periodic table?

  • ordered by increasing atomic number
  • elements in same group (column) have same no. of outer shell electrons
  • elements in same period (row) have same no. electron shells
• how many electrons are in the outer shell of a group 1 element?


  one
• why do elements in the same group have similar chem properties?

  • have the same number of electrons in the outer shell
• what groups of the periodic table are the alkali metals?

  group 1
• list two properties of alkali metals

  • relatively low melting points
  • soft
• why are group 1 elements called the alkali metals?

  they react with water to form alkaline solutions (pH greater than 7)
• what are the products of the reaction between lithium and water?

  lithium hydroxide and hydrogen
• write a balanced symbol equation for the reaction of sodium with water 


  $2Na\ +$$\ 2H_2O\ ->\ 2NaOH\ +$$H_2$
• why should alkali metals be stored in oil?

  to prevent them from reacting with water vapour + oxygen in air
• what would be observed when lithium reacts with water?

  • slowest reaction of alkali metals
  • bubbles of hydrogen = produced
  • doesn't melt (highest MP of alkali metals)
• what would be observed when sodium reacts with water?

  • faster reaction than lithium
  • floats on surface of water (less dense than water)
  • bubbles of hydrogen = produced: cause sodium to whizz around surface of water
  • melts because enough energy = given out to meet sodium's melting point
• what would be observed when potassium reacts with water?

  • more violent reaction than sodium
  • bubbles of hydrogen = produced which cause the potassium to whizz around surface of water
  • melts into a shiny ball
  • burns with a lilac flame
• what is the order of reactivity of the first 3 alkali metals with water?

  • lithium = least violent reaction
  • potassium = most violent
  • lithium < sodium < potassium
• using the reaction of the first 3 alkali metals with water, predict the reactivity trend down group 1

  • reactivity increases down group 1
• why does reactivity increase down group 1?

  • number of electron shells increases down group
  • so more electron shielding
  • weaker attraction between positive nucleus and outer shell electron
  • means = easier to remove outer shell electron to form a positive metal ion
• which group 1 element would you expect to react most violently with water?

  reactivity increases down group

  • so francium = most violent reaction with water
• what group are the halogens in? why?

  • group 7
  • because they have 7 outer electrons
• what is the colour and state of chlorine at room temperature?


  pale green gas
• what is the colour and state of bromine at room temperature?


  red-brown liquid
• why are the halogens at different states at room temperature?What is the trend down the group?

  • at room temp: chlorine = gaseous, bromine = liquid, iodine = 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 state would you expect the halogens fluorine and astatine to be at room temperature?

  • Fluorine = above chlorine so should have a boiling point lower than chlorine
  • means that it would be a gas at room temperature
  • Astatine = 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 temp
• why does melting and boiling point increase down group 7?

  • molecules get bigger down the group so there are more intermolecular forces to overcome during melting/ boiling
  • so more energy is required
• what is the chemical test for chlorine?

  • damp litmus paper placed into a test tube of gas
  • if chlorine= present, litmus paper will turn red then white due to the bleaching effect of chlorine
• halogens are diatomic. What does this mean?

  • they form molecules consisting of 2 atoms
• what charge does a halide ion carry? Why?

  -1

  • they gain one electron to have a stable electron configuration
• what is produced when a halogen reacts with a metal?

  metal halide salt
• write a balanced symbol equation for the reaction between bromine and sodium


  $Br_2+$$2Na->2NaBr$
• write a balanced symbol symbol equation for the reaction between chlorine and calcium


  $Cl_2+$$Ca->CaCl_2$
• predict the product of the reaction between magnesium and fluorine

  magnesium fluoride (MgF$_2$)
• write a word equation for the reaction between iodine and potassium

  iodine + potassium -> potassium iodide

  • remember the ion of a halogen ends with -ide
• 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
• what is formed when hydrogen reacts with a halogen?

  hydrogen halides e.g HCl, HBr
• 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 halide dissolves in water?

  • an acidic solution
  • hydrogen ions dissociate
  • making the solution acidic
• write a balanced symbol equation for the reaction between hydrogen and chlorine


  $H_2+$$Cl_2->\ 2HCl$
• predict the product of the reaction between hydrogen and fluorine

  hydrogen fluoride (HF)
• when does a halogen displacement reaction occur?

  • when a more reactive halogen displaces a less reactive halogen from an aqueous solution of its halide
• why will halogen A only be displaced by halogen B if B is above A in group 7?

  • the most reactive halogen (B) will displace the less reactive halogen (A) to become part of the ionic compound
  • Reactivity increases as you go up the group so B must be higher in group & to be more reactive than A
• 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