4. inorganic chemistry and the periodic table Flashcards
what do group 2 metals form when they react
2+ ions
what happens to the atomic radius of group 2 metals down the group
it increases due to increased electron shells
what happens to the reactivity of group 2 metals down the group
it increases due to increased shielding
what happens to first ionisation energy of group 2 metals down the group
it decreases due to greater atomic radius and increased shielding
what happens when group 2 metals react with water
produces a metal hydroxide and hydrogen.
what happens when group 2 metals react with chlorine gas
they form metal chlorides ( white precipitate)
what happens when group 2 metals react with oxygen
they form oxides
what happens when strontium and barium react with excess oxygen and heat energy
they form metal peroxides
what happens when group 2 metals react with dilute acids
produces hydrogen gas and solutions of metal compounds
what happens when group 2 hydroxides react with dilute acid
they form a salt and water - neutralisation
what happens to the solubility of group 2 hydroxides down the group
they increase
what happens to the solubility of group 2 sulfates down the group
they decrease
what can you use to test for sulfate ions
barium chloride, it reacts to form barium sulfate which is a white precipitate
what group 2 metals undergo thermal decompositions
group 2 carbonates and nitrates
how does thermal decomposition occur
heating the substance in lots of oxygen
what do group 2 carbonates produce when they undergo thermal decomposition
carbon dioxide and a metal oxide which forms as a white powder
what do group 2 nitrates produce when they undergo thermal decomposition
nitrogen dioxide and oxygen with a metal oxide which forms as a white powder
what is required as you go down group 2 for thermal decomposition
more heat as the ions increase in size and thermal stability increases.
how do group 1 carbonates react in thermal decomposition
they dont decompose upon heating in a lab as they require extremely high temperatures
how do group 1 nitrates react in thermal decomposition
they produce a metal nitrite and oxygen.
what group 1 element decomposes in the same way as group 2 elements
lithium
explanation of thermal stability trend down groups 1 and 2
as you go down the group they form more stable carbonates and nitrates so they require more energy to undergo thermal decomposition.
what happens to the charge density as you go down group 1 and 2
it decreases as the ionic radius increases as you go down but the charge stays the same so the charge density decreases.
how to carry out a flame test
- nichrome wire and clean it in concentrated HCL then into a blue flame
- repeat the cleaning until no colour is produced in the flame
- dip the wire into the unknown metal compound and place it into the flame
- observe the colour produced
flame colour of lithium
red
flame colour of sodium
orange/yellow
flame colour of potassium
lilac
flame colour of magnesium
no colour
flame colour of calcium
brick red
flame colour of strontium
crimson red
flame colour of barium
pale green
how do the colours in the flame tests occur
electron transitions:
when energy is supplied by heat, the electrons move to orbitals with higher energy then drop back down to their original orbital. this produces energy in the form of light.
the amount of energy released during this is shown through a unique wavelength that produces the colour.
if the wavelength produces a colour not on the visible spectrum you will not see a colour emitted.
what are group 7 elements
halogens, highly reactive non metals
what happens to the atomic radius of group 7 elements down the group
it increases due to additional electron shells
what happens to the electronegativity of group 7 elements as you go down the group
decreases as the atomic radius and electron shielding increases meaning the outer electrons are less strongly attracted to the nucleus and can be removed easier
what happens to the melting and boiling points down group 7
it increases. they are simple covalent molecules that are held together by london forces. as the relative atomic mass increases, the amount of london forces increases meaning more energy is required to overcome them.
what happens to reactivity down group 7
it decreases due to the increased distance from the nuclei to the outer electrons, this increases atomic radius and increased shielding makes it harder to attract electrons to react.
why are group 7 good oxidising agents
the oxidising power decreases down the group so the halogen will replace the halide beneath it. cl2 can displace br- and br2 will displace i-
what is a halide ion
a negative ion of a halogen
halide ions are good reducing agents what happens to reducing power down the group
it increases a electrons are easier to lose and they form larger ions due to shielding and larger atomic radius
how to distinguish halide ions
- add acidified silver nitrate
Cl- white precipitate
Br- cream precipitate
I- yellow precipitate
Can be tested further by using dilute and concentrated ammonia
what happens when a hydrogen halide reacts with ammonia gas
forms ammonia salts
what happens when hydrogen halides react with water
form dilute acids
how to test for sulfate ions
acidified barium chloride - white precipitate produced. barium sulfate
how to test for carbonate and hydrogencarbonate
add HCl - bubbles produced
collect gas and bubble through limewater, limewater turns cloudy if CO2 is present
test for ammonium ions
add NaOH and gently warm to produce ammonia gas. hold damp red litmus paper over the substance and it will turn blue if ammonium ions are present
