The halogens (Gr 7) - ES Flashcards
What does fluorine look like at room temp
colourless gas
What does chlorine look like at room temp
pale green gas
What does bromine look like at room temp
brown/red liquid
What does iodine look like at room temp
silver/black solid
What trends happens down the halogens
colour gets darker, melting point and boiling point increase : they are less volatile and switch from gas to liquid to solid as intermolecular bonds get stronger
Halogens solublity
they are not very soluble in water but much mores soluble in organic solvents
Halogens as elements characteristics
they exist as diamotic molecules, they are in the p-block on the periodic table and outer shell for all is s²p⁵
Chemical properties of halogens
to achieve noble gas configuration a halogen atoms has to gain one electrons which means they are oxidising agents. Oxidising power increases going up the group
How is oxidising power affects up the group of halogens
it increases because the incoming electron is closer and less shielded from the positive nucleus so attraction is stronger
Halogens with metals
the halogens form an ionic compound. They fully gain an extra electron, becoming halide ions
Halogens with non-metals
the halogens share electrons, forming a covalent bond
Cl⁻ colour
colourless
Br⁻ colour
colourless
I⁻ colour
colourless
Cl₂ in aqueous solution colour
very pale green
Br₂ in aqueous solution colour
orange
I₂ in aqueous solution colour
brown
Cl₂ in organic solvents colour
pale green
Br₂ in organic solvents colour
brown
I₂ in organic solvents colour
purple
A halogen higher in the group is ale to …
oxidise (react with) the halide ion of a halogen lower in the group
How to see clearly the colour difference in halogens
an organic solvent is added and the mixture is shaken, the organic solvent and water do not mic so 2 layers form. Halogen molecules are non-polar so dissolve better in the upper, organic layer (also non-polar) giving it a characteristic colour which is more distinctive to see
Tests for halides in solution
add silver nitrate (AgNO) and then to check shake with aqueous ammonia solution
Fl⁻ and AgNO observation + formula + ionic equation
no precipitate
Cl⁻ and AgNO observation + formula + ionic equation
white precipitation, AgCl (silver chloride)
Ag⁺ + Cl⁻ -> AgCl
Br⁻ and AgNO observation + formula + ionic equation
cream precipitation, AgBr (silver bromide)
Ag⁺ + Br⁻ -> AgBr
I⁻ and AgNO observation + formula + ionic equation
yellow precipitation, AgI (silver iodide)
Ag⁺ + I⁻ -> AgI
What happens to silver halides when left in the sun
they start to go grey/black due to formation of silver as they are light sensitive
What happens when AgCl is shaken with aqueous ammonia solution
completely redissolves
What happens when AgBr is shaken with aqueous ammonia solution
partially redissolves
What happens when AgI is shaken with aqueous ammonia solution
does not redissolve
Risks of using chlorine
very toxic and any leak can be dangerous as it is a gas so will spread quickly
Uses of chlorine
water treatment (drinking and pools) to kill germs, make household bleach, extract bromine from sea water, make HCl
