Electronic Configuration & Reactivity (Edexcel IGCSE Chemistry: Double Science)

Chemical properties of elements in the same group

• Elements in the same group in the Periodic Table will have similar chemical properties
• This is because they have the same number of outer electrons so will react and bond similarly
• The group number of an element which is given on the Periodic Table indicates the number of electrons in the outer shell
  • This rule holds true for all elements except helium; although is in Group 0, it has only one shell, the first and innermost shell, which holds only 2 electrons

• We can use the group number to predict how elements will react as the number of outer shell electrons in an element influences how the element reacts.
• Therefore, elements in the same group react similarly
  • By observing the reaction of one element from a group, you can predict how the other elements in that group will react
  • By reacting two or more elements from the same group and observing what happens in those reactions you can make predictions about reactivity and establish trends in reactivity in that group

• For example, lithium, sodium and potassium are in Group 1 and can all react with elements in Group 7 to form an ionic compound
• The Group 1 metals become more reactive as you move down the group while the Group 7 elements show a decrease in reactivity moving down the group

• The elements in Group 0 of the Periodic Table are called the noble gases
• Noble gases are:
  • Non-metals
  • Monatomic (exist as single atoms)
  • Colourless and non-flammable gases at room temperature
• Most elements participate in reactions to complete their outer shells by losing, gaining, or sharing electrons
• Group 0 elements do not do this because they have full outer shells of electrons 
  • They are therefore unreactive (inert) and do not form molecules easily
• Most noble gases have 8 electrons in their outer shell, except helium which has 2
• Electronic configurations of the noble gases:
  • He = 2
  • Ne = 2, 8
  • Ar =  2, 8, 8
  • Kr =  2, 8, 18, 8
  • Xe = 2, 8, 18, 18, 8

The noble gases

Noble gases are located in the last group on the right hand side of the Periodic Table