35 (a) Consider the first ionization of aluminum (Al), the minimum energy requir

Question

35 (a) Consider the first ionization of aluminum (Al), the minimum energy required to ionize one mole of gaseous aluminum atom to its gaseous cation was found to be 577 kJ mol (i) Determine the effective nuclear charge (Zef) experienced by the outermost (ii) Also, evaluate the Screening factor (S) of the inner electron(s) electron(s) (5 marks) (b) Gallium (Ga), thallium (TI) and aluminum (Al) are in the same Group. Consider the following first ionization energies for gallium (Ga) and thallium (TI) elementFi First ionization energies (kJ mol1 577 590 Ga TI (i) Determine the effective nuclear charge (Zetf)experienced by the outermost electron(s) of Ga and T Compare the Zeff values of Al, Ga and TI, and briefly account for your finding (ii) 5 marks) 36 (a) Dihydrogen molecule (H2) would undergo a single-electron reduction to form dihydrogen anion (Hz) H2(g) e. H2"(g) + Discuss briefly why such dihydrogen anion should be stable for existence (3 marks) (b) Some physical data of H', H2 and He' are given in the table below molecule bond distance bond dissociation 1.06 0.74 1.08 (kJ mol1 255 432 322 He2 Given the electron affinity of hydrogen 73 ki mor, estimate the Hnn of the single-electron reduction of dihydrogen. Instead of a single value, you may present an energy range within which the H should reside (7 marks)

Explanation / Answer

35. for aluminium

electronic configuration : 1s2 2s2 2p6 3s2 3p1

(i) Zeff for outermost electron of Al = Z - S = 13 - 9.5 = 3.5

Z = atomic number

(ii) screening factor (S) for outermost electron of Al = 2 x 0.35 + 8 x 0.85 + 2 x 1 = 9.5

(b) for Ga and Tl

Electronic configuration of Ga = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p1

Electronic configuration of Tl = 1s2 2s2 2p6 3s2 3p6 3d10 4s2 4p6 4d10 5s2 5p6 4f14 5d10 6s2 6p1

(i) Zeff (Ga) = 31 - 26 = 5

Zeff (Tl) = 81 - 74 = 7

(ii) screening factor (S) for Ga = 2 x 0.35 + 18 x 0.85 + 10 x 1 = 26

screening factor (S) for Tl = 2 x 0.35 + 18 x 0.85 + 58 x 1 = 74

So the Zeff increases as the size of element increases from Al to Ga to Tl.

Related Questions

Navigate

• Browse (All)
• Browse 3
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.