Topic 4- Inorganic Chemistry And The Periodic Table Flashcards
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Describe the trend in ionisation energy down group 2
- Nuclear charge increases
- Number of filled inner shells increases the level of repulsion
- Introduction of new quantum shell increases repulsion
- Increase in atomic radii
OVERALL: DECREASE
What are the reasons for the trend in reactivity for Group 2 elements?
Reactivity increases down the group as the atomic radii increase there is more shielding. The nuclear attraction decreases and it is easier to remove (outer) electrons and so cations form more easily
What are the reactions of Mg to Ba when reacted with oxygen?
2Mg + O2 -> 2MgO
2Ba + O2 -> 2BaO
What are the reactions of group 2 elements between Mg to Ba when reacted with chlorine?
Mg + Cl2 -> MgCl2
Ba + Cl2 -> BaCl2
What is the reaction of group 2 elements from Mg to Ba when reacted with water?
Mg + 2H2O -> Mg(OH)2 + H2
Ca + 2H2O -> Ca(OH)2 + H2
What is the special reaction of magnesium and steam?
Mg(s) + H2O(g) -> MgO (l) + H2 (g)
What is the reaction of oxides with dilute acid?
MgO (s) + 2HCl (aq) -> MgCl2 + H2O
CaO (s) + H2SO4 (aq) -> CaSO4 (aq)+ H2O (l)
what is the reaction of hydroxides with dilute acid?
2HNO3 (aq) + Mg(OH)2 -> Mg(NO3)2 (aq) + 2H2O
2HCl (aq) + Mg(OH)2 (aq) -> MgCl2 (aq) +2H2O (l)
what are the trends in solubility of the hydroxides and sulfates
- Solubility of group 2 hydroxides become MORE soluble down the group.
if not soluble, hydroxides appear as white precipitates - Group 2 sulfates become LESS soluble down the group (e.g. MgSO4 (most soluble) and BaSO4 (least) as barium sulfate is used to test for sulfate ions in a solution
what is thermal stability?
how stable a compound is when heated
what reasons are there to explain the trends in thermal stability of nitrates and carbonates of elements in group 1 and 2?
A small 2+ ion has a lot of charge packed into a small volume of space. It will have a HIGH CHARGE DENSITY and will have a marked distorting effect on any negative ions which are nearby.
A larger 2+ ion has the SAME charge spread over a larger volume of space. LOWER CHARGE DENSITY, less distortion to nearby negative ions.
describe thermal stability of a group 1 and 2 carbonate ion
the positive ion attracts delocalised electrons in the carbonate ion towards itself = polarised.
When heated, it decomposes, releasing CO2 from the metal oxide.
The amount of heat depends on how polarised the ion is…. HIGHLY POLARISED = LESS HEAT
how is a characteristic flame colours by Group 1 and 2 compounds formed ?
In a flame test, heat causes the electron to move to a HIGHER ENERGY LEVEL.
- The electron is unstable at the higher energy level so it drops back down.
- As it drops down an energy level, energy is emitted as visible light within the wavelength of observed light.
what are the flame colours of group 1 compounds?
- Li = red
-Na = orange/yellow - K = lilac
- Rb = red/purple
- Cs = blue/violet
what are the flame colours of group 2 compounds?
Be = n/a
Mg = n/a
Ca= brick red
Sr= crimson red
Ba = apple green
Name the experimental procedure to show:
1- patterns in thermal decomposition of group 1 and 2 nitrates and carbonates
2- flame colours in compunds of group 1 and 2 elements
METHOD- NICHROME WIRE
- nichrome (or platinum) is an unreactive metal and will not give off any flame colour
1. clean the wire by dipping it in concentrated HCl acid
2. heat in a bunsen flame
3. ensure the sample is grinded and powdered
4. hold the end of the wire and dip wire in the solid and place in the bunsen flame and observe the colour made
reasons for the trend in MP and BP for group 7 elements
INCREASES down the group
molecules and their electron clouds become larger, greater no of electrons therefore greater London forces between molecules
As the intermolecular forces of the instantaneous dipole - induced dipole attraction therefore more energy is needed to overcome these forces.
describe the physical state and electronegativities of group 7 halogens
Physical state
- F2 = gas
- Cl2= gas
- Br2= liquid
- I2= solid
Electronegativity DECREASES down the group (due to the increase of inner electron shells and increase in distance from the nucleus)
what is the trend of reactivity of group 7 halogens
LESS REACTIVE DOWN THE GROUP
- atoms become larger, outer electrons further away from the nucleus
- outer electrons are shielded more from the attraction of the positive nucleus due to MORE inner electrons
- harder to attract electrons to form an ion
Describe the trend of reactivity of group 7 elements in terms of redox reactions of Cl2, Br2 and I2
DECREASES DOWN THE GROUP
- Group 7 elements cause the oxidation of other compounds -> a good oxidising agent
- Elements gain electrons LESS readily so their oxidising power DECREASES, therefore a more reactive halogen will displace a less reactive one.
understand in terms of changes in oxidation number
i oxidation reactions between group 1 and 2
metals
when halogens react they’re reduced and they oxidise other substances
in an oxidation reaction, they produce halide salts
e.g. Mg (s) + Cl2 (g) -> MgCl2 (s)
magnesium is oxidised: 0 -> +2 chlorine is reduced: 0 -> -1
ii -the disproportionation reaction of chlorine with water and the use of chlorine in water treatment
Cl2 (g) + H2O (l) -> HCl (aq) + HClO (aq)
oxidation: Cl2 -> 2Cl- + 2e- oxidation state: 0-> +1
reduction: Cl2 + 2e- -> 2Cl- oxidation state: 0->-1
(hypochlorus acid ionises to make chlorate (I) ions aka hypochlorite ions)
iii- the disproportionation reaction of chlorine with cold, dilute aqueous sodium hydroxide to form bleach
2NaOH (aq) + Cl2 (g) -> NaClO (aq) + NaCl (aq) + H2O (l)
oxidation: Cl2 -> 2Cl- + 2e-
(oxidation number: 0 -> 1+)
reduction: Cl2 + 2e- -> 2Cl-
(oxidation number: 0 -> -1)
iv- the disproportionation reaction of chlorine with hot alkali
3Cl2 + 6NaOH -> 5NaCl + NaClO2 + 3H2O
0 1-
0 5+
oxidation: Cl2 -> 10e- + 2Cl+5
reduction: Cl2 +2e- -> 2Cl-
