The Halogens Flashcards Preview

AS Chemistry > The Halogens > Flashcards

Flashcards in The Halogens Deck (13)
Loading flashcards...

Physical properties of halogens

Most reactive non metallic group
Found as stable halide ions, dissolved in sea water, combined as solid deposits with sodium


Trends in boiling point

RTP, diatomic molecules
Increase in boiling point die to more electrons, stronger London forces, more energy needed to break LF, increase BP


Halogen colours

F2, pale yellow
Cl2, pale green gas
Br2, red brown liquid
I2, shiny grey black solid
At2, never seen


Redox reactions

Halogen atom reduced, gains one electron to form 1- halide with config of nearest noble gas
Oxidising agent gets reduced


Halogen halide displacement reaction

Shows reactivity of halogens decrease down group
Halogen displaces halide from solution, colour change if halogen more reactive
Add cyclohexane to make colours more vivid
Colour present shows displaced halogen
Oxidation number changes


Results of halogen halide displacement reaction

Chlorine reacted with Br-, I-
Bromine reacted with I-
Iodine has not reacted


Reactivity of fluorine, astatine

Fluorine reacts with almost any substance that it come in contact with
Astatine has never been seen, least reactive


Trends in reactivity

Redox reactions, halogens react by gaining e-
Down group, atomic radius increases, more inner shells so shielding increases, less nuclear attraction to capture an electron from another species, reactivity decreases
Become weaker oxidising agents down group



Redox reaction in which same element is oxidised and reduced


Reaction of chlorine with water

Chlorine used in water purification
Chloric (I) acid is a weak bleach
Add indicator to chlorine and water solution
Initially goes red, then bleaches

Cl2(aq) + H2O(l) => HClO(aq) + HCl(aq)


Reaction of chlorine with cold sodium hydroxide

Cl2(aq) + 2NaOH(aq) => NaClO(aq) + NaCl(aq) + H2O(l)

Resulting solution has large concentration of chlorate (I) ions from NaClO
Solution is a household bleach


Benefits of chlorine

Beneficial in asking water os drinkable after natural disasters, prevent typhoid, cholera


Risks of chlorine

Extremely toxic
Respiratory irritant
If reacted with organic hydrocarbons, chlorinated hydrocarbons formed, cause cancer