Reactivity Trends Among Group 17 Halogens

Practical – Trends in the Periodic Table

Reactivity of the group 7 elements - the halogens

Ref: Saunders N. 2000, Creative Chemistry

You have seen that the Group 1 alkali metal elements increase in reactivity as you go down the group. Sodium is less reactive than potassium, which is less reactive than rubidium (which you weren’t allowed to observe directly!) Today, you will use displacement reactions to work out the order of reactivity of the Group 17 halogen elements using Chlorine, Bromine and Iodine.

Hypothesis:

I predict that in order of reactivity of the three it will be Chlorine, Bromine than Iodine. They are all in the same group 17 (Halogens) but in different periods which has an effect on the elements properties such as the electronegativity decreasing. Chlorine is the most electronegative so it will steal

Cl2 (Chlorine Water) + KBr (potassium bromide)→ KCL( potassium chloride) + Br2 ( Chlorine)

Cl2 (Chlorine Water) + KI (potassium iodide)→ KCL( potassium chloride) + I2 ( Iodine)

Br2 (Bromine Water) + KI (potassium iodide)→ KBr( potassium bromide) + I2 ( Iodine)

Write the electron configuration for each halogen tested, using subshell notation. Contrast the similarities and differences in the configurations.

Chlorine 1s2 2s2 2p6 3s2 3p5 or [Ne] 3s2 3p5 . Bromine 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p5 [Ar] 4s2 3d10 4p5 & Iodine 1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p5 or [Kr] 5s2 4d10 5p5

Each element is one electron of having a full valence shell and they all have 5 electrons in their P shell.

Write the order of reactivity for the halogens, from most to least reactive.

In order of most reactive to least reactive it is Fluorine, Chlorine, Bromine, Iodine, Astatine

Describe the trend in reactivity of the Group 17 elements compared to their order on the periodic