Topic 4 - Inorganic Chemistry Flashcards
(31 cards)
Trend in Ionisation Energy down group 2
Ionisation energy decreases down group 2
This is because both the atomic radius and shielding increases which means there is greater distance between the positive nucleus and the negative outer electrons and therefore there are weaker forces of electrostatic attraction. The increase in the number of protons and therefore the nuclear charge is overriden by the effect of shielding
Trend in reactivity down Group 2
Reactivity increases since ionisation energy decreases due to increase in atomic structure and shielding. Therefore less energy is required to break the electrostatic forces of attraction between the positively charged nucleus and the negatively charged outer electron
Group 2 + Water
React to form metal hydroxides/bases
Reactivity increases down the group (no reaction with Be)
Mg reacts slowly with cold water but vigorously with steam and produced MgO instead of a hydroxide
Group 2 + Oxygen
React to form metal oxides/bases
Redox reaction - oxygen is reduced and metal is oxidised
Group 2 oxides are white solids
Group 2 + Chlorine
React to form metal chlorides
Redox reaction - chlorine is reduced and metal is oxidised
Group 2 oxides + Water
Form bases and alkaline solutions
–> Oxides react readily with water to form hydroxides which dissociate to form OH- ions (except for Be which will not react with water)
Group 2 oxides / hydroxides + Dilute Acid
Both Group 2 oxides and hydroxides are bases and therefore can neutralise acids
acid + base –> salt + water
Trend in solubility of Group 2 Sulfates
Sulfates are -2 charged and therefore decrease in solubility as you go down the group
Trend in solubility of Group 2 Hydroxides
Hydroxides are -1 charged and therefore increase in solubility as you go down the group
Trend in thermal stability of nitrates and carbonates of elements in group 2 in terms of size and charge of cations
Group 2 carbonates and nitrates can decompose upon heating
- Carbonates break down into metal oxides and carbon dioxide (via thermal decomposition)
- nitrates break down into metal oxides, nitrogen dioxide and oxygen (via thermal decomposition)
Both carbonates and nitrates become more thermally stable as you gown down the group
Carbonate and nitrate ions have a large electron cloud that can be distorted when nearby +group2 ions - as you go down the group, the group 2 metals become larger in size and therefore their charge is spread out over a larger area and they have a lower charge density and therefore they distort the carbonate/nitrate less
Trend in thermal stability of nitrates and carbonates of elements in group 1 in terms of size and charge of cations
Group 1 Carbonates are thermally stable under a bunsen flame (except for Lithium carbonate which will form an oxide and carbon dioxide)
Group 1 Nitrates break down into nitrates and oxygen upon heating (except LiNO3 which decomposes to form Li2O, NO2 and O2)
Testing Thermal Decomposition of Group 1 and 2 Nitrates
Nitrates (NO3-)
- We can measure how long it takes a specific amount of oxygen to be produced. Using a gas syringe or the amount needed to relight a glowing splint
- The length of time it takes until a specific amount of NO2 is produced (brown gas - can easily be observed, but is toxic so must be done in a fume cupboard)
Testing Thermal Decomposition of Group 1 and 2 Carbonates
Carbonates (CO32-)
- 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 produced - could use a gas syringe
Flame colours in compounds of Group 1 and 2 element
Test for positive ions / cations
We get different colours because electrons in shells move to higher energy levels as they absorb energy from the flame. When they drop back to lower energy levels, light is released. Different colours are produced as the difference in energy levels determines the wavelength of light released
- Dip the nichrome wire in HCL
- Dip in sample
- Place loop into blue bunsen flame and observe flame
Crimson - Li+
Yellow/Orange - Na+
Lilac - K+
Red - Rb+
Blue - Cs+
Dark red - Ca2+
Crimson - Sr2+
Green - Ba2+
Halogens - Group 7 elements
Fluorine - pale yellow gas
Chlorine - pale green gas
Bromine - Brown/Orange liquid
Iodine - grey solid
Boiling Point of Group 7
Boiling point increases down the group - this is because the London forces increases due to increasing size and relative mass of atoms - therefore physical state goes from gas at top of group to solid at bottom
Electronegativity Trend group 7
Electronegativity is the ability for an atom to attract a bonding pair of electrons in a covalent bond
Electronegativity decreases down the group - because the atoms get larger (atomic radius increases and shielding increases) therefore the distance between the positive nucleus and bonding electrons increase + there is also more shielding
Reactivity of Group 7 elements
Reactivity of the halogens decreases down the group
This is because there is an increase in atomic mass and electron shells - so the atoms are larger as you go down the group. Therefore, the attraction of the outer electron to the nucleus decreases
Displacement reactions between halogens and halide ions in aqueous solution, followed by addition of organic solvent
A more reactive halogen will displace a less reactive halide ion
- Reactivity of halogens decrease down the group - atomic radius is smaller so attracts electrons better than larger atoms
- Halogens also less oxidising as we go down the group
- Halogen will displace a halide from solution if the halide is lower in the periodic table
Displacement reactions between halogens and halide ions in aqueous solution, followed by addition of organic solvent
Adding an organic solvent (hexane) to halogens can make it easier to observer colour changes
- The halogen present will dissolve readily in the organic solvent
- Forms a layer above the aqueous layer and a coloured band will appear
What are the actual reactions between halide ions and halogens
Chlorine water + Potassium chloride (NO REACTION)
Chlorine water + Potassium bromide
(yellow aqueous layer and orange organic layer)
Cl2 + 2Br- –> 2Cl- + Br2
Chlorine water + Potassium iodide
(brown aqueous layer and purple organic layer)
Cl2 + 2I- –> 2Cl- + I2
Bromine water + Potassium chloride (NO REACTION)
Bromine water + Potassium bromide (NO REACTION)
Bromine water + Potassium iodide
(brown aqueous layer and purple organic layer)
Iodine solution + Potassium chloride (NO REACTION)
Iodine solution + Potassium bromide (NO REACTION)
Iodine solution + Potassium iodide (NO REACTION)
colours of halogens and halide ions
Potassium chloride/bromide/ iodine = colourless
Chlorine water - yellow
bromine water - orange
iodine solution - brown
Halogen + Group 1 and 2 Elements
Form metal halides - redox reactions
- metal is oxidised and halogen is reduced
Halogens react with cold alkalis in disproportionation reactions
Disproportionation reacts are where there is a simultaneous reduction and oxidation of halogen
- makes a salt with 1 oxygen
- eg - sodium bromate (1)
