O-LevelChemistryAtomic Structure5070/22 · Oct/Nov 2019 · Q810 Marks

Phosphorus is an element in Group V of the Periodic Table.

(a)(i)One of the isotopes of phosphorus is: ³¹P Deduce the number of electrons, neutrons and protons in this isotope of phosphorus. number of electrons number of neutrons number of protons[3]
(a)(ii)What is the meaning of the term isotopes?[1]
(b)Phosphorus reacts with potassium chlorate(V) to form potassium chloride and phosphorus(V) oxide. Complete the equation for this reaction. ... KClO3 + ... P → ... KCl + ... P2O5[1]
(c)The structure of a compound of phosphorus is shown. [Diagram: O || H—O—P—O—P—O—P—O—H || || O—H O—H] Deduce the molecular formula of this compound.[1]
(d)Phosphorus reacts with chlorine to form phosphorus trichloride, PCl3. Draw a dot-and-cross diagram for a molecule of phosphorus trichloride. Only include the outer shell electrons.[2]
(e)The equation for the reaction of phosphorus with copper(II) ions is shown. 2P + 5Cu2+ + 8H2O → 5Cu + 2PO43- + 16H+ Identify the oxidising agent. Explain your answer. oxidising agent: explanation:[2]

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Mark scheme

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

[1] electrons: 15
[1] neutrons: 16
[1] protons: 15
[1] atoms with the same number of protons and different numbers of neutrons / atoms of the same element with different numbers of neutrons
[1] 5KClO3 + 6P → 5KCl + 3P2O5
[1] H5P3O10
[1] one pair of bonding electrons between the P and each of the three Cl atoms and 2 non-bonded electrons on P
[1] 6 non-bonded electrons on each Cl
[1] Cu2+ / copper ions
[1] it gains electrons

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