In this I/GCSE Chemistry Blog post, we will be understanding the main points of the Halogens group, as well as the reactions that takes place for Group 7.
Group 7- The Halogens
Element- Atomic number-colour-state at RT-boiling point
Chlorine- 17- green- gas- -34
Bromine- 35- red brown - liquid -59
Iodine- 53-dark grey-solid-185
In group 7 the fewer number of electrons the more reactive, as the outer shell is closer to the nucleus and the force of attraction is stronger.
- Halogens can combine with hydrogen to for, hydrogen halides . When hydrogen chloride dissolves in water the molecules split up this is called dissociation.
- The solution formed is called hydrochloric acid and its acidic.
- If HCl is dissolved in an organic solvent like methylbenzene meaning it doesn't dissociate so it's not acidic.
Make sure that if you test it will litmus paper that there is no moisture as if there is it will dissociate and it will behave like an acid.
Displacement Reactions
Elements in group 7 take part in displacement reactions- a more reactive element displaces a less reactive element from a compound.
KCL colourless + Cl2 colourless/ Br2 orange/ I2 brown = no reaction
KBr colourless +Cl2 colourless/ Br2 orange/ I2 brown= Orange Br2/ NR/ NR
Kl colourless + Cl2 colourless/ Br2 orange/ I2 brown = brown I2/brown I2/ NR
EQUATION FORM: Cl2 + 2KI —• I2 + 2KCl
- Each chlorine gains an electron to form chlorine ions.
- Iodine lose an electron to form neutral iodide.
- Loss of electron = oxidation Gain of electron= reduction (OIL RIG)
- In displacement reaction oxidation and reduction happen simultaneously. An oxidising agent get reduced and a reducing agent gets oxidised.
- This is known as a redox reaction.
That is all for this blog!
