alkali metals and the halogens and the noble gases Flashcards
what elements are in the noble gases - group 0
helium neon argon krypton xenon radon
name some uses of the noble gases
helium:
used in party balloons, weather balloons and air ships because it is low density and is lighter than air so it will float
neon:
emits light when current passes through it
advertisement signs
argon:
light bulbs, unreactive so the bulb can get very hot
why are the noble gases unreactive?
they all have a full outer shell of electrons
what elements are in the group 1?
lithium sodium potassium rubidium caesium
name some properties of the alkali metals group 1
soft
low density
very reactive
what is the word and symbol equation for the alkali metals reaction with oxygen?
EG- sodium + oxygen –> sodium oxide
EG- 4Na + o2 –> 2 Na2O
what colours does the flame of a Bunsen burner turn with the alternative reaction of the alkali metals and oxygen?
lithium - red
sodium - yellow-orange
potassium - lilac
what happens when lithium reacts with water? what is seen, symbol and word equation.
fizzes and floats on the surface, turns U.I purple
word equation:
lithium + water –> lithium hydroxide + hydrogen
symbol equation:
2Li + 2 H2O –> 2LiOH + H2
what happens when sodium reacts with water? what is seen, symbol and word equation.
fizzes and floats to the surface, turns U.I purple
turns into a molten ball
word equation:
sodium + water –> sodium hydroxide + hydrogen
symbol equation:
2Na + 2 H2O –> 2NaOH + H2
what happens when potassium reacts with water? what is seen, symbol and word equation.
fizzes and floats to the surface, turns U.I purple
catches fire with a lilac flame
word equation:
potassium + water –> potassium hydroxide + hydrogen
symbol equation:
2K + 2 H2O –> 2KOH + H2
why are the alkali metals stored under oil?
to keep them from reacting with oxygen and moisture in the air
what happens to the melting points of the alkali metals down the group?
decrease
what happens to the hardness of the alkali metals down the group?
decrease
what happens to the reactivity of the alkali metals down the group?
increase
what safety precautions must be taken when reacting the alkali metals with water?
safety glasses
safety screen
small piece of metal
handle metal with tweezers
why are group 1 called the alkali metals?
they all form a alkaline solution when they react
what is the test for hydrogen?
place a lit splint over the gas
popping sound with be heard if gas is present
why do alkali metals get more reactive down the group?
they want to lose the outer most electron, the easier it is to do this the more reactive they are. down the group there is greater shielding as the electron is further away. the effective nuclear charge decreases and electron is lost easier
what happens to the melting point down group 7, the halogens?
increases
why does reactivity decrease down the group?
they need to gain 1 electron, the harder it is for the element to gain one electron, the less reactive it is. the outer most electrons are further away from the effective nuclear charge down the group and there is more shielding from inner orbitals, this makes the nuclear charge less effective at gaining an electron.
name some uses of the halogens
chlorine:
added to drinking water, swimming pools and plastics because its poisonous and kills bacteria
iodine:
antiseptic because it kills bacteria
what colours are the halogens in a displacement reaction?
fluorine - pale yellow, gas
chlorine - yellow/ green, gas
bromine - orange/ brown, liquid
iodine - grey/ black, solid
word and symbol equation for alkali metal reacting with halogens
sodium + fluorine –> sodium fluoride
Na + Cl2 –> 2KCl
what is a displacement reaction?
when a more reactive element displaces a less reactive element from its compound
