O-LevelChemistryAtomic Structure5070/22 · May/June 2014 · Q1010 Marks

Astatine, At, is an element in Group VII of the Periodic Table. The table shows some information about two isotopes of astatine. [Table with rows for 210/85At and 211/85At. Columns for 'symbol', 'number of protons', 'number of electrons', 'number of neutrons'.]

(a)(i)Complete the table. | symbol | number of protons | number of electrons | number of neutrons | |---|---|---|---| | 210/85At | | | | | 211/85At | | | | [2][2]
(a)(ii)What is meant by the term isotopes? .[1][1]
(b)Astatine forms a diatomic molecule with the same type of bonding as in a chlorine molecule. Draw the 'dot-and-cross' diagram for an astatine molecule. Only draw the outer shell electrons. [1][1]
(c)(i)Astatine reacts with magnesium to form magnesium astatide, MgAt₂, which contains Mg2+ and At- ions. Describe how a magnesium ion and an astatide ion are formed from a magnesium atom and an astatine atom. .[2][2]
(c)(ii)Predict two physical properties of magnesium astatide. 1. 2. .[2][2]
(d)(i)Bromine reacts with aqueous magnesium astatide. Construct the ionic equation for this reaction. .[1][1]
(d)(ii)Explain why astatine does not react with aqueous magnesium iodide. .[1][1]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (May/June 2014). The mark or mark type is shown in brackets.

[1] B10 (a) (i) 210/85At: protons 85, electrons 85, neutrons 125 (1)
[1] (a) (i) 211/85At: protons 85, electrons 85, neutrons 126 (1)
[1] (a) (ii) Atoms with same atomic number and different mass number / atoms with same number of protons and different number of neutrons / atoms with same atomic number and different nucleon number / atoms of the same element with different numbers of neutrons / nucleons (1)
[1] (b) Correct 'dot-and-cross' diagram (1) IGNORE: inner shell electrons ALLOW: electrons to be all dots or all crosses
[1] (c) (i) Magnesium loses electrons and astatine gains electrons / magnesium transfers electrons to astatine (1)
[1] (c) (i) Correct numbers lost / gained: 2 electrons (lost from magnesium) 1 electron gained (by astatine) (1)
[1] (c) (ii) Any two (1 mark each) from: High melting point / high boiling point Does not conduct electricity as a solid Conducts electricity when molten / conducts electricity in solution ALLOW: Soluble in water
[1] (c) (ii) (Second property)
[1] (d) (i) Br2 + 2At¯ → 2Br¯ + At2 (1) ALLOW: correct multiples / fractions IGNORE: state symbols
[1] (d) (ii) Astatine is less reactive (than iodine) (or reverse) / iodide ions are more difficult to oxidise (than astatide ions) (or reverse) (1)

On Oracle Prep you can write or photograph your own answer and have it marked by AI against this mark scheme, with feedback on what you missed.