OCR Advanced GCE in Chemistry/Periodic Table: Transition elements/Answers

1. Half filled or filled sub-shells are most stable so are favoured at expense of 4s sub-shell only containing 1 electron (see page for more info)

2. A transitional element is defined as a d-block element forming one or more stable ions with incompletely filled d-orbitals e.g. zinc and scandium are not transitional metals because they can't form ions with partially filled d-orbitals

3. They form ions with partially filled d-orbitals which can absorb light

4. green. therefore absorbs red approx 650nm

5. rust coloured gelatinous precipitate

6. dichlorotetraamminechromium(lll) ion

7. [Cu(H2O)6]2+(aq) + 4Cl-(aq) ---> [CuCl4]2-(aq) + 6H2O(l)

450nm Blue absorbed, Yellow observed (λ 600nm) so use blue filter - use graph to determine the ratio when colour is first fully yellow

[CuCl4]2-(aq) + 4NH3(aq) + 2H2O(l) ---> [Cu(NH3)4(H2O)2]2+(aq) + 4Cl-(aq)

580nm Yellow absorbed, Dark blue observed (λ 430nm) use blue filter

8. 82.4%