Halogens Flashcards
What group are the halogens located in?
Group 7 (starting with F) which are diatomic molecules.
How does boiling point change down group 7?
It increases because they have more electrons so the induced dipole dipole forces are stronger.
What state are Cl2, I2 and Br2 at room temperature?
Cl2 is a gas, Br2 is a liquid and I2 is a solid.
What is the outer electronic shell coniguration of the halogens?
s2, p5
What ions do halogens make in reactions.
1- when reduced.
How does reactivity change down group 7?
It decreases. So fluorine is the most reactive
Explain why reactivity decreases down group 7 (the halogens)?
Due to electron affinity decreasing. The incoming electron is further from the nucleus and experiences greater shielding, so is less attracted to the nucleus of the atom.
What is electron affinity?
The energy required for one mole of gaseous atoms to gain an electron for form one mole of gaseous 1- ions.
Eg: X(g) + e- = X-
What factors affect electron affinity?
Atomic radius, shielding and neuclear charge.
What is a disproportination reaction and give the two needed examples.
Where the same species is oxidised and reduced in the same reaction.
Eg: Cl2 + H2O = HCl + HClO (chlorine into water for purification)
Cl2 + 2NaOH = NaCl + NaClO + H2O (making bleach)
What are the dangers of Cl2?
It is a toxic gas.
Can react with hydorocarbons to create chlorinated hydrocarbons which are dangerous.
1. Right of people to choose its usage
2. Consideration of other purification options
Describe the chemical test to detect HALIDE IONS
Adding nitric acid to prevent any carbonates from creating a false positive by reacting with the silver ions. Then drop by drop adding silver nitrate solution. Each halide ion will react with aqueous Ag+ to form a solid precipitate.
So we add silver nitrate solution.
Cl-(aq) + Ag+ = AgCl(s)
Br-(aq) + Ag+ = AgBr(s)
I-(aq) + Ag+ = AgI(s)
What is the colour of the AgCl precipitate?
White
What is the colour of the AgBr precipitate?
Pale cream
What is the colour of the AgI precipitate?
Pale yellow
