Inorganic chemistry and the Periodic Table Flashcards
What is the trend in ionisation energy for group 2?
Decreasing
As you descend Group 2, there are more shells of electrons, so the outer shell electron being removed is further from the nucleus + more shielded (this outweighs the increase in nuclear charge). Therefore attraction to the nucleus decreases
What is the trend in atomic radius in group 2 (and 1)?
Increasing
More shells of electrons + more shielding so electron are further away from nucleus + less tightly held therefore atom gets bigger
What is the trend in reactivity in group 2 (and group1)?
Reactivity increases/gets more vigorous
As you go down the group, the number of shells of electrons increases
- So the outer electron being lost is further from the nucleus and more shielded (this outweighs the increased nuclear charge)
- Therefore, the electron is more easily lost and the element is more reactive
What are the trends in solubility of hydroxides and sulphates for group 2?
Hydroxides - more soluble down the group
Sulfates - less soluble down the group
What is the trend in thermal stability of nitrates and carbonates?
As you go down group 2, the thermal stability increase
- The size of the cation increases
- So polarises the anion less
What is the trend in group 1 for nitrates and carbonates?
All group 1 nitrates decompose when strongly heated
What does lithium nitrate decompose to form? Why?
4LiNO3 → 2Li2O + 4NO2 + O2
Lithium is so strongly polarising that it causes the nitrate ion to break down
Why do the other group 1 nitrates melt rather than fully decompose?
2NaNO3 → 2NaNO2 + O2
This is because the other group 1 cations have a lower charge density so are not as strongly polarising
Why does only lithium carbonate decompose?
Li2CO3 → Li2O + CO2
Lithium is so strongly polarising that it causes the carbonate ion to break down. However other Group 1 carbonates will not decompose when heated, as the cations are not strongly polarising enough
What is the reaction of Group 2 metals with chlorine:
Metal + chlorine → metal chloride (salt)
What is the reaction of Group 2 metals with water:
Metal + water → metal hydroxide + hydrogen
What is the reaction of Group 2 metal oxides with water:
Metal oxide + water → metal hydroxide
What is the reaction of Group 2 metal oxides with acids:
Metal oxide + acid → metal salt + water
What is the reaction of Group 2 hydroxides with acids:
Metal hydroxide + acid → metal salt + water
Describe the method for a flame test:
- Clean a platinum or nichrome wire by heating it in a non-luminous Bunsen burner flame, dipping it into a little concentrated hydrochloric acid on a watch glass and heating it again. Continue this until the wire produces little or no colour in the flame
- Dip the clean wire into the acid and then into a small portion of powdered compound on a watch glass.
- Hold the wire so that the powdered solid is in the edge of the flame and note any colour change
- Observe the flame through a diffraction grating or direct vision spectroscope
What are the different colour of flames:
Calcium - Orange
Magnesium - no colour
Lithium - Crimson Red
Barium - apple green
Sodium - Yellow
Potassium - lilac
What are the origins of colour in the flame test?
- Energy provided by the flame allows an electron to be ‘excited’
- This configuration is unstable, so the electron will return to its original energy level (relaxation)
- Extra energy will then be emitted in the form of light
- The difference in energy between the different electron shells determines the wavelength and therefore colour of the light emitted
Why do some elements not have colour?
- The energy provided is not sufficient to excite an outer shell electron between energy levels
- The light emitted might have a wavelength which is not in the visible range of light
Why do some elements not have colour?
- The energy provided is not sufficient to excite an outer shell electron between energy levels
- The light emitted might have a wavelength which is not in the visible range of light
What are the appearances for the different halogens:
Chlorine - pale yellow gas
Bromine - reddish brown liquid
Iodine - grey solid/purple vapour
What is the trend for the boiling points?
Down the group - boiling point increases
The London forces between the molecules of the halogen get stronger as there are more electrons/a bigger Mr. So it takes more energy to overcome them
Explain the trend for reactivity of halogens:
Reactivity decreases
- Down the group, more shells of electrons therefore shielding + distance from the nucleus increase
- This outweighs the increases nuclear charge
- Therefore there is a weaker attraction of outer electron to the nucleus - so harder to gain an electron
What is the trend for electronegativity of halogens?
Down the group, electronegativity decreases (harder to attract an electron)
- Distance from nucleus increases (more shells of electrons)
- Shielding increases
- These 2 factors outweigh the increased nuclear charge
- So the attraction to the nucleus is weaker
Why is iodine a better reducing agent than bromine?
Iodine reduces the sulphur the furthest, so it is the best reducing agent/has the most reducing power
What is the test for sulphate ions:
Add acidified barium chloride
Result = white ppt forms
(HCl added first will remove any OH- or CO32- ions that would also give a white ppt)
What is the test for halide ions:
Add acidified silver nitrate
Result = Cl- = white ppt, Br- = cream ppt, I- = yellow ppt
The precipitates form because silver halides are insoluble
Test for carbonate ions:
Result = effervescence (of CO2), limewater turns cloudy
What happens when chlorine reacts with water:
Cl2 + H2O -> HCl + HOCl
Disproportionation
What happens when chlorine react with cold dilute sodium hydroxide?
Cl2 + 2NaOH -> NaCl + NaOCl + H2O
Disproportionation
What happens when chlorine react with hot concentrated alkali?
3Cl2 + 6NaOH -> NaClO3 + 5NaCl + 3H2O
Disproportionation
What happens when hydrogen halides react with ammonia?
HCl + NH3 -> NH4Cl
What happens when hydrogen halides react with water?
HBr + H2O -> H3O+ + Br-
What happens when solid KCl react with concentrated sulphuric acid?
KCl + H2SO4 -> HCl + KHSO4
No further reaction occurs
What happens when solid KBr halide react with concentrated sulphuric acid?
KBr + H2SO4 -> HBr + KHSO4
2HBr + H2SO4 -> Br2 + SO2 + 2H2O
