Note Summary - Groups PDF

Noble Gases The elements in Group 0 of the periodic table are called the noble gases. They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons. The noble gases have eight electrons in their outer energy level, except for helium, which has only tw...

Noble Gases The elements in Group 0 of the periodic table are called the noble gases. They are unreactive and do not easily form molecules because their atoms have stable arrangements of electrons. The noble gases have eight electrons in their outer energy level, except for helium, which has only two electrons The boiling points of the noble gases increase with increasing relative atomic mass (going down the group). Group 1: the Alkali Metals Reactions of Group 1 The elements in Group 1 of the periodic table o Group 1 metals react in a similar way as o all have 1 electron in their highest they all have 1 electron in their outer shell energy level o react with non-metals to form ionic o are metals with low density (the first compounds in which the metal ion carries a three elements in the Group are less charge of + 1. The compounds are white dense than water) solids which dissolve in water to form o are stored under oil to prevent them colourless solutions. from reacting with oxygen or water. o e.g. 2 Na + Cl2  2NaCl Reaction with water Increasing Reactivity down the Group o Group 1 metals react with water releasing In group 1, the further down the group an element hydrogen and form hydroxides which is the more reactive it becomes. dissolve in water to give alkaline solutions. As the atoms get larger the outer electron is (this is why they are known as alkali metals) further from the nucleus. o They react vigorously with water fizzing and Thus the outer electron is less attracted to the moving around on the surface of the water. nucleus and so can more easily be lost. o e.g. 2Na + 2H2O  2NaOH + H2 Group 7: The Halogens The elements in group 7 of the periodic table : o all have 7 electrons in their highest energy level o have coloured vapours. (These are toxic vapours) o consist of molecules which are made up of pairs of atoms (Cl2, Br2 ,I2 ) o form ionic salts with metals in which the chloride, bromide or iodide ion (halide ion) carries a charge of -1 o form molecular (simple covalent) compounds with other non-metallic elements. Trends in Group 7 In Group 7, the further down the group an element is: o the higher its relative molecular mass o the higher its melting point and boiling point (due to increased intermolecular forces. See 4.2 bonding and structure for more detail) o the less reactive the element. Displacement Reactions Decreasing Reactivity down the A more reactive halogen can displace a less reactive halogen Group from an aqueous solution of its salt. Going down the group: Cl2 + 2 NaBr  Br2 + 2 NaCl or Cl2 + 2Br - Br2 + 2 Cl- The atoms get bigger  in this reaction an orange colour of Br2 would appear and so outer shell electrons are Cl2 + 2 NaI  I2 + 2 NaCl or Cl2 + 2I- I2 + 2 Cl- further from nucleus Br2 + 2 NaI  I2 + 2 NaBr or Br2 + 2I- I2+ 2 Br – Outer electrons less strongly attracted to nucleus  in these two reactions a brown colour of I2 would appear can less easily gain electrons. N Goalby chemrevise.org 6