Inorganic Chem and the Periodic Table Flashcards
What ions do Group 2 elements form when they react?
+2 ions
They lose 2 electrons and have electron configurations ending in s2
How does extra shells have an affect on the atomic radius?
Extra shells added as we go down group 2
The atomic radius increases as we go down group 2
What is the trend in ionisation energies in group 2 and explain why this happens
decreases
as the atomic radius increases and extra shells are added as we go down group 2, so the outer electrons are further from the nucleus and there is more shielding so there is a weaker attraction between the outer electrons and the nucleus
both of these make it easier to remove the outer electron and so less energy is needed to remove one
What do you use to test for halide ions?
Acidified AgNO3
Why does an increase in the number of protons, so therefore increase in + charge, not have an effect on ionisation energies?
The shielding effect overrides an increase in positive charge
When group 2 elements react with water to form?
What is the general equation for this?
bases
a reaction with water may form a metal hydroxide
M(s) + 2H2O(l) –> M(OH)2(aq) +H2(g)
What is the reactivity trend (with water) in group 2?
Which element react slowly and which element is the exception?
Be is the exception- since no reaction happens
Increases down the group
Mg- very slow
Be- exception
Explain the reasons for the trend in reactivity in group 2
Atom gets larger and electron is further from nucleus. Easier to remove and hence more reactive. There is more shielding
What happens when group 2 metals and cold water react?
they form metal oxides, group 2 metal oxides are white solids
What do group 2 elements form when they react with chlorine and what is the general equation for the reaction?
metal chlorides
M(s) + Cl2(g) –> MCl2(s)
What do group 2 oxides form when reacted with water
bases
Alkaline solutions
What is the trend in alkaline strength down group 2
They become more strongly alkaline as we go down the group as the hydroxides become more soluble.
What happens when oxides react with water
Oxides react readily with water to make hydroxides which dissociate to form OH- ions
What is the reaction like between
Magnesium oxide and water
Beryllium oxide and water
Magnesium oxide reacts very slowly and the hydroxide barely dissolves
Beryllium oxide doesn’t react with water at all and the hydroxide is insoluble
What is the general reaction between group 2 metals and HCl?
M(s) + 2HCl(aq) –> MgCl2(aq) +H2(g)
What is the general reaction between group 2 metals and H2SO4?
M(s) + H2SO4 __> MSO4(aq) + H2(g)
What is the type of reaction when group 2 oxides and hydroxides react with acids?
Neutralisation
If the anion has a single charge (e.g. hydroxides) what is the trend in solubility?
increasing
Mg(OH)2 is slightly soluble
Ba(OH)2 creates a strong alkaline solution
If the anion has a double charge (e.g. sulfates) what is the increase in solubility?
decreasing
BaSO4 is the least soluble
What is the equation for when carbonates break down via thermal decomposition?
MCO3(s) –> MO(s) + CO2(g)
What is the equation for when nitrates break down via thermal decomposition?
2M(NO3)2(s) –> 2MO(s) + 4NO2(g) + O2(g)
What is the trend in thermal stability in group 2 carbonates/ nitrates?
increases going down group 2
Explain the trend in thermal stability in group 2 carbonates?
Group 2 carbonates are more thermally stable as you go down the group
Cations get bigger so therefore have less of a polarising effect and distort the carbonate ion less
As the C-O bond is not weakened as it is much harder to break down
explain the reason for the trend of thermal stability in group 1 carbonates
group 1 carbonates do not decompose except for lithium
this is because they don’t have a big enough charge density to polarise the carbonate ion as they only form 1+ ions
however the lithium ion is small enough to have a polarising effect so therefore lithium carbonate can decompose
Which is more thermally stable group 1 compounds or group 2 compounds?
group 1
What happens when carbonates are under a Bunsen flame?
they are thermally stable
Give the equation for Lithium carbonate decomposing
Li2Co3 (s) –> Li2O(s) + CO2(g)
What do nitrates break down into?
nitrites and oxygen
What is the equation for KNO3 breaking down?
2KNO3(s) –> 2KNO2(s) + O2(g)
Give the formula for a nitrate ion
NO3-
Give the formula for a nitrite ion
NO2 3-
What are the two ways to test thermal stability for nitrates
1) measure how long it takes for a specific amount of oxygen to be produced. Use a gas syringe. Or relight a glowing splint
2) the length of time it takes until a specific amount of NO2 is produced.
What is the risk of using NO2
brown gas that is toxic
How would you test the thermal stability of a carbonate?
the length of time it takes until a specific amount of CO2 is produced. CO2 turns limewater cloudy so the quicker this turns cloudy, the more CO2 is produced. Could use a gas syringe
May also see fizzing
What is the method for conducting a flame test
Dip nichrome wire in concentrated HCl (to sterilise)
Dip it into the sample
Place the loop into the blue bunsen flame and observe the colour
what is the reason for the trend of thermal stability of group 2 nitrates
the ease of thermal decomposition decreases down group 2 and this is because down the group the ions get larger and therefore have less charge density
which means there is less polarisation of the nitrate anion and less weakening of the N-O bond
What are the flame test results/ colours for: Lithium Sodium Potassium Rubidium Caesium Magnesium Calcium Strontium Barium
crimson red orange-yellow lilac red blue No flame- energy emitted is outside visible spectrum brick red red apple green
How do we get different colours in flame tests?
Electrons in the shells move to higher energy levels as they absorb energy from the flame.
When they drop back down to lower energy levels, light is released.
Different colours are produced as the difference in energy levels determines the wavelength of light released
list 2 properties of the halogens
low melting and boiling points
exist as diatomic molecules
Describe the states of F, Cl, Br and I
F- pale yellow gas
Cl- pale green gas
Br- brown-orange liquid
I- grey solid but brown in water, and violet in cyclohexane
What can be added to make colour changes easier to see in halogen displacement reactions
Organic solvents, e.g. hexane
What happens between the halogen and organic solvent
halogen present will dissolve readily in the organic solvent which forms a layer above the aqueous layer- a coloured band will appear