A-LevelChemistryAtomic structure9701/23 · May/June 2019 · Q112 Marks

(a) A sample contains three different types of atom: 48Ar, 49K and Ca. (i) State fully, in terms of the numbers of subatomic particles, what these three atoms have in common. [1] (ii) State fully, in terms of the numbers of all subatomic particles, how these three atoms differ from each other. [1] (b) A sample of sulfur contains only two isotopes, 32S and 34S. The relative atomic mass of this sample is 32.09. isotope isotopic mass 32S 32.0 34S 34.0 Calculate the percentage abundance of the isotopes present in this sample. % abundance 32S = % abundance 34S = [3] (c) The electronic configuration of a sulfur atom is 1s22s22p63s²3p4. (i) Identify which orbital in a sulfur atom has the lowest energy. [1] (ii) Sketch the shape of a p orbital. [1] (iii) During the process of ionisation a sulfur atom loses an electron. S(g) → S+(g) + e¯ ΔΗ = 1000 kJ mol-1 Identify the orbital from which this electron is removed. Explain your answer. orbital explanation [2] (d) (i) Complete the diagram to show the arrangement of electrons within the third shell of a phosphorus atom. 3s 3p [1] (ii) Explain why the first ionisation energy of sulfur is less than that of phosphorus. [2] [Total: 12]

(a)(i)State fully, in terms of the numbers of subatomic particles, what these three atoms have in common.[1]
(a)(ii)State fully, in terms of the numbers of all subatomic particles, how these three atoms differ from each other.[1]
(b)A sample of sulfur contains only two isotopes, 32S and 34S. The relative atomic mass of this sample is 32.09. isotope isotopic mass 32S 32.0 34S 34.0 Calculate the percentage abundance of the isotopes present in this sample. % abundance 32S = % abundance 34S = [3]
(c)(i)Identify which orbital in a sulfur atom has the lowest energy.[1]
(c)(ii)Sketch the shape of a p orbital.[1]
(c)(iii)During the process of ionisation a sulfur atom loses an electron. S(g) → S+(g) + e¯ ΔΗ = 1000 kJ mol-1 Identify the orbital from which this electron is removed. Explain your answer. orbital explanation[2]
(d)(i)Complete the diagram to show the arrangement of electrons within the third shell of a phosphorus atom. 3s 3p[1]
(d)(ii)Explain why the first ionisation energy of sulfur is less than that of phosphorus.[2]

Mark scheme

Marking points from the official mark scheme (May/June 2019). The mark or mark type is shown in brackets.

[1] All have the same nucleon number OR same sum / total number of protons + neutrons
[1] (different) number of protons, neutrons and electrons
[3] M1 x/ 100 × 32 + (100-x/100 × 34) = 32.09
[3] M2 (32x + 3400 – 34x) = 3209 so x = 95.5
[3] M3 S32 95.5% AND S34 4.5%
[1] 1s
[1] [Diagram of a p-orbital]
[2] M1 3p
[2] M2 It is less attracted to the nucleus (so takes less energy to lose) OR It is the highest energy orbital (which is occupied) / it is in the highest energy orbital
[1] [Diagram showing correct electron arrangement for 3s and 3p in Phosphorus]
[2] M1 (in S, the electron is removed from the) 2 electrons in (3)p orbital OR a pair of electrons in (3)p (orbital / sub-shell)
[2] M2 (paired electrons) repel

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