Group 2 Flashcards
Describe and explain the trend, down the group, of the reactivity of Group 2 with water. (5)
- reactivity increases
- atomic radii increases
- more shielding
- increased nuclear charge
- ionisation energy decreases
Why are the second ionisation energies of calcium and strontium greater than their first ionisation energies? (1)
- ion is smaller
Explain why barium is more reactive than calcium. (4)
- Barium atoms are larger
^ more shielding - outweighs the increase in nuclear charge
- ionisation energy decreases
Which Group 2 oxide produces a saturated solution with the highest pH?
BaO(aq)
State how a Group 2 element forms an ionic bond with non-metals.
- by donating its 2 outer electrons
Are group 2 elements oxidising or reducing agents?
reducing.
Explain the trend in first ionisation energies as you move down Group 2. (4)
- decreases
- nuclear charge same
- shielding increases
^ leads to weaker attraction between the nucleus & the outermost electrons
Describe the trend in alkalinity as you move down Group 2. (1)
- increases
Describe the trend in the reactions of Group 2 with water. (1)
- react more vigorously w/ water as you go down the group
Explain the trend in the first three ionisation energies of magnesium. (3)
- ionisation energy increases
- similar shielding
- large increase b/w 2nd and 3rd IE because 3rd electron is being removed from 2p orbital rather than 3s orbital
Explain how the trend in solubility and strength as a base observed going down Group 2 are connected. (3)
- solubility in water & strength as a base both increase down the Group
- increasing solubility means that there’s more OH- ions in the solution
- base strength is measured by the concentration of OH- ions.
Explain how the bonding in Beryllium Chloride differs from the rest of the Group 2 Chlorides. (4)
- predominantly covalent
- Be2+ = highest mass-charge ratio
- so Be2+ polarises the Cl ion
- causing the Cl ion to share its electron
Give the reagents required to test for and distinguish between the halide ions. (4)
- dilute nitric acid
- silver nitrate solution
- dilute ammonia
- concentrated ammonia
Define: disproportionation reaction
- a reaction in which the same species is simultaneously oxidised and reduced.
Suggest why adding chlorine to the drinking water is safe to do so. (2)
- it’s only added in small volumes
- therefore not harmful to humans in those levels
Define: reducing agent
- a species that can donate electrons
Explain why an iodide ion is a better reducing agent than a bromide ion. (3)
- an iodide ion is larger
- therefore outermost electrons more shielded by inner shells
- so outermost e- lost more easily
Describe the test for: sulfate ions
- add a few drops of aqueous barium chloride
- if sulfate ions present, a white precipitate (barium sulfate) is formed
Describe the test for: ammonium ions
- react w/ warm aqueous sodium hydroxide
- ammonia will turn damp litmus paper blue
Explain why fluorine has a lower b.p than chlorine. (2)
- flourine = smaller than Cl
- forces b/w flourine molecules = weaker
Predict the order of melting points for: (6)
- chlorine (Cl)
- iodine monochloride (ICl)
- sodium chloride (NaCl)
- Cl = lowest m.p , NaCl = highest m.p
- Cl = weak induced dipole-dipole forces only
- ICl = polar molecule w/ permanent dipole-dipole forces between molecules
- permanent d.ps stronger than induced d.ps but weaker than ionic bonds in NaCl
- NaCl = strong ionic bonds b/w ions
- ionic bonds = strongest of all bonds present
Explain why bromine is a liquid at room temperature but fluorine and chlorine are gases. (3)
- Br = higher b.p than F & Cl
- more electrons in molecules of Br
- so more energy required to pull Bromine molecules apart
Explain the different boiling points of NH3, F2 and Br2. (5)
- NH3 = hydrogen bonding b/w molecules
- F2 & Br2 = both induced d.p-d.p
^ induced d.ps in Br2 = stronger bcs Br2 has more electrons - induced d.p force in Br2 = stronger than hydrogen bonding in NH3
- hydrogen bonding in NH3 stronger than induced d.ps in F2
State one advantage and one disadvantage of using chlorine in water treatment. (2)
advantage:
- Cl kills bacteria
disadvantage:
- Cl is toxic
Explain why iodine is a weaker oxidising agent than bromine. (3)
- I = larger atomic radius
- & more shielding
- I has a weaker nuclear attraction
Explain why it’s important NOT to add any household cleaning agents that contain hydrochloric acid to a solution of bleach. (2)
- NaClO reacts with HCL to produce chlorine gas
- which is toxic
