Group 7: Reactivity & Electronic Configurations (Edexcel IGCSE Chemistry (Modular))
Revision Note
Electronic configuration of Group 7 elements
When halogen atoms gain an electron during reactions, they form -1 ions called halide ions
We can use electronic configuration to explain the trends in chemical reactivity down Group 7
Electronic configuration of Group 7 elements
The atoms of the elements of Group 7 all have 7 electrons in their outer shell
Reactivity of Group 7 non-metals decreases as you go down the group
As you go down Group 7, the number of shells of electrons increases, the same as with all other groups
However, halogen atoms form negative ions when they gain an electron to obtain a full outer shell
This means that the increased distance from the outer shell to the nucleus as you go down a group makes the halogens become less reactive
Fluorine is the smallest halogen, which means its outermost shell is the closest to the positive nucleus of all the halogen
Therefore, the ability to attract an electron is strongest in fluorine making it the most reactive
As you move down the group, the forces of attraction between the nucleus and the outermost shell decreases
This makes it harder for the atoms to gain electrons as you descend the group
Therefore, the halogens are less reactive the further down the group you go
Examiner Tip
Exam questions on this topic occur often so make sure you know and can explain the reactivity trends of the Group 7 elements in detail, using their electron configurations.
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