Sunday, March 1, 2009

igcse free - chemistry notes / Metals and Non-Metal

Properties of Metals
conduct heat
conduct electricity
hard and strong
Non Metals
do not conduct electricity
do not conduct heat
not magnetic
Alkali Metals
very reaction (have to be stored under oil to prevent reaction with air)
form ions with 1+ charve.
soft and can be cut with a knife
potassium and sodium float on water
Trends down the group
atomic size increases (increased no of electrons and shells)
lose outer shell electron to form 1+ charged ions. Therefore reactivity increases as you go down the group. The electron is farther away from the nucleus.
melting points decrease
alkali metals with oxygen in the air
Sodium + Oxygen = Sodium Oxide
4Na + O2 -> 2NaO2
alkali metals with water
gives off hydrogen gas
resulting solution is alkali
Sodium + Water -> Sodium Hydroxide + Hydrogen
2Na + 2H20 -> 2NaOH + H2
alkali metals with halogens
they react rapidly with halogens
Sodium + Chlorine -> Sodium chloride
2Na + Cl2 -> 2NaCl
non metals
form ions with 1- charge
very reactive
as you go down the group the colour of vapour becomes darker
fluorine - yellow
chlorine - green
bromine - red
iodine - violet
Halogens are used as bleaching agents
Trends as you go down the group
atomic size inicreases
reactivity decreases (easier to gain electrons when electron shell is closer to the nucleus)
melting and bioling point increase
halogens with hydrogen
Chlorine + Hydrogen -> hydrogen chloride (hydrochloric acid)
Cl2 + H2 -> 2HCl
halogens with metals (forms a salt)
Magesium + Bromine -> Magnesium bromide
2Mg + Br2 -> 2MgBr
Displacement Reactions with Halogens
A more reactive halogen will displace a less reactive one.
Example: chlorine can displace bromine from potassium bromide, but cannot displace fluorine from potassium fluoride.
Cl2 + 2KBr -> 2KCl + Br2 (chlorine displaced bromine)
Br2 + 2KI -> 2KBr + I2 (bromine displaced iodine)
Br2 + 2KF -> 2KF + Br2 (bromine can't displace fluorine)
Noble Gasses
gasses at room temperature
density with increase in atomic size
Argon is used inside light bulbs
Helium is used in hot air ballons
boiling point increases as you go down the group
Transition Metals
hard dense metals
not very reactive
often used as catalysts
have variable valency (different charges, Fe2+ Fe3+)
Some metals form oxides in reaction to oxygen
some metals form basic oxides
some non-metals form acidic oxides
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