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%