C1 pages 108-110
group 1 elements
group 7 elements
group 0 elements
They are known as alkali metals
Includes lithium, sodium, potassium, rubidium, caesium and francium
they all have one electron in their outer shell which makes them very reactive and gives them similar properties.
They are all soft and have a low density
the trends as you go down group 1 include
Increasing reactivity
higher relative atomic mass
lower melting and boiling points
the outer electron is more easily lost as the attraction between the nucleus and electron decreases, because the electron is further away from the nucleus the further down the group.
reactions with water
lithium, sodium and potassium float and move around the surface, fizzing furiously.
they react vigorously
they produce hydrogen
the lower down the group (the more reactive) an alkali metal is, the more violent the reaction
the amount of energy given out when they react increases down the group. for potassium and below there is enough energy to ignite hydrogen.
they also form hydroxides that dissolve in water to give alkaline solutions
reactions with chlorine
react vigorously when heated in chlorine gas to form white salts called metal chlorides
as you go down the group reactivity increases so therefore the reaction with chlorine gets more vigorous.
reactions with oxygen
lithium reacts to form lithium oxide
group 1 metals react with oxygen to form a metal oxide, different types of oxide will form depending on the group 1 metal.
sodium reacts to form a mixture of sodium oxide and sodium peroxide
potassium reacts to form a mixture of potassium peroxide and potassium superoxide
alkali metals form ionic compounds with non-metals
the group 1 elements don't need much energy to lose their one outer electron to form a full outer shell, so they readily form 1+ ions
its so easy for them to lose their outer electron that they will only ever to form ionic compounds
these are generally white solids that dissolve in water to form colourless solutions
they are known as the halogens
all non-metals with coloured vapours (all exist as molecules which are pairs of atoms)
chlorine
bromine
iodine
fluorine
very reactive, poisonous yellow gas
fairly reactive, poisonous dense green gas
dense, poisonous, red-brown volatile liquid
dark grey crystalline solid or purple vapour
trends as you go down group 7 include
have higher melting and boiling points
higher relative atomic mass
become less reactive
its harder to gain an extra electron, because the outer shell is further from the nucleus
all react in similar ways because they all have 7 electrons in Their outer shell
halogens can form molecular compounds
halogens can share electrons via covalent bonding with other non metals so as to achieve a full outer shell. the compounds that form when halogens react with non metals all have simple molecular structures
halogens form ionic bonds with metals
the halogens form 1- ions called halides when they bond with metals
the compounds that form have ionic structures
more reactive halogens will displace less reactive ones
a displacement reaction can occur between a more reactive halogen and the salt of a less reactive one.
chlorine can displace bromine and iodine from an aqueous solution of its salts (a bromide or iodide). bromine will also displace iodine because of the trend in reactivity
known as noble gases
all inert, colourless gases (at room temp)
include the elements helium, neon and argon
they all have eight electrons in their outer energy level, apart from helium which has two, giving them a full outer shell. as their outer shell is energetically stable they don't need to give up or gain electrons to become more stable. this means they are more or less inert (they don't react with much at all).
they exist as monatomic gases (single atoms not bonded to each other)
because they are inert they are non-flammable
patterns in properties of the noble gases
the boiling points increase as you move down the group along with increasing relative atomic mass
the increase in boiling point is due to an increase in the number of electrons in each atom. therefore there are greater intermolecular forces between them which need to be overcome.