What are the properties and trends of Group 7 elements? All pupils will be able to (Baseline): Describe the trends in properties in Group 7 Most pupils will be able to (Further): Use the displacement reactions to prove the order of reactivity for the halogens is correct Some pupils will be able to (Challenge): Explain the reactivity of the halogens with reference to their size

http://www.bbc.co.uk/education/clips/zm94 d2p (2min clip about reactivity and outer shell) Higher Triple explanation, stop at 2min Watch the video and make notes on the properties of the halogens.

Will the Fluorine or the Chlorine get the Electron from the Sodium? Why?

What did we find out? What is the Order of Reactivity of the Halogens? Most Reactive Least Reactive S I Z E R E A C T I V Y Fluorine (F) Chlorine (Cl) Bromine (Br) Iodine (I) Astatine (At)

The Halogens The halogens want to grab an electron but it has to get past all the other electrons in the way F Cl Br I As Group 7 – The Halogens

Its all about getting close to the nucleus Iodine has 53 electrons in the way of its nucleus Bromine has 35 electrons in the way of its nucleus Chlorine has 17 electrons in the way of its nucleus Fluorine has 9 electrons in the way of its nucleus

I have learnt that: The halogens all form ions with a single negative charge in their ionic compounds with metals. The halogens form covalent compounds by sharing electrons with other non-metals. A more reactive halogen can displace a less reactive halogen from a solution of one of its salts. The reactivity of the halogens decreases going down the group.

Plenary Questions Write word and symbol equations for the displacement reactions of: Potassium Bromide and Chlorine Sodium Iodide and Fluorine Would reaction a or b happen the most quickly do you think? Why? Use ideas about electron configurations to explain the order of reactivity of the halogens.

Plenary Questions Write word and symbol equations for the displacement reactions of: Potassium Bromide and Chlorine Sodium Iodide and Fluorine a) Potassium Bromide + Chlorine Potassium Chloride + Bromine a) 2KBr + Cl2 2KCL + Br2 b) Sodium Iodide + Fluorine Sodium Fluoride + Iodine b) 2NaI + F2 2NaF + I2

Plenary Questions Would reaction a or b happen the most quickly do you think? Why? Reaction b would happen the most quickly. This is because there is a bigger gap between the reactivity of these two Halogens. Therefore Fluorine will displace Iodine more quickly than Chlorine would displace Bromine.

Plenary Questions Use ideas about electron configurations to explain the order of reactivity of the halogens. The Halogens become less reactive as you go down group 7. This is because to get a full outer shell, the Halogens need to gain an electron. To do this it must attract the electron from another atom. The closer the outer shell is to the nucleus, the more attracted the electron will be to the Halogen. Therefore large Halogen atoms find it difficult to attract the electron that it needs, and this makes them less reactive. Small Halogen atoms are much more attractive to electrons and react much more vigorously (quickly).