Edexcel IGCSE Chemistry 复习笔记 1.4.4 Electronic Configuration & Reactivity

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 (valence electrons)
  • 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 valence 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 metals show a decrease in reactivity moving down the group

• The elements in group 0 of the periodic table are called the noble gases
• They are all non-metal, monatomic (exist as single atoms), colourless, non-flammable gases at room temperature
• The group 0 elements all have full outer shells of electrons; this electronic configuration is extremely stable
• Elements participate in reactions to complete their outer shells by losing, gaining, or sharing electrons
  • The Group 0 elements do not need to do this, because of their full outer shells which makes them unreactive and inert

   

• Other than helium which has 2 electrons in its outer shell, the noble gases have eight valence electrons (which is why you may see this group labelled “group 8”)
• 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 periodic table highlighting the noble gases – they occupy the group furthest to the right 

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