OCR A Jan 2012 Paper 1 Q3 (with explained solutions) |

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OCR A Jan 2012 Paper 1 Q3

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The modern Periodic Table is arranged into blocks of elements based on their electron configuration. (a) We now know that electrons are in shells; shells have sub-shells and sub-shells have orbitals. (i) Explain what is meant by the term orbital.[1] (ii) Complete the electron configuration below, in terms of sub-shells, for an atom of sulfur. 1s2[1] (iii) How many full orbitals are in an atom of sulfur?[1] (b) One mole of sulfur atoms has a mass of 32.1 g. What is meant by one mole of substance?[1] (c) Ionisation energies provide evidence for the order of elements in the modern Periodic Table. Define the term first ionisation energy.[3]OCR 2012<br />
(d) The first ionisation energies and atomic radii of F, Ne and Na are shown below. element first ionisation energy / kJ mol1 atomic radius / nm Ne Na 1681 2081 496 0.071 0.065 0.191 (i) Explain why there is an increase in first ionisation energy between F and Ne.[3] (ii) Explain why there is a decrease in first ionisation energy between Ne and Na.[3] [Total: 13]OCR 2012 Turn over<br />

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F321 Question 3 (a) (i) A region (within an atom) that can hold (up to) two electrons (cid:57) (with opposite spin) Answer Mark Scheme Marks (ii) 1s22s22p63s23p4 (cid:57) (b) (iii) 7 (cid:57) (The amount of substance which contains) as many particles as there are carbon atoms in 12g of 12C (atoms) (cid:57) (c) Energy (needed) to remove an electron (cid:57) from each atom in one mole (cid:57) of gaseous atoms (cid:57) 1 1 1 January 2012 Guidance ALLOW can be found OR contains OR has etc. for can hold ALLOW area OR volume OR space OR somewhere etc. for region DO NOT ALLOW path of an electron IGNORE references to orbitals being parts of sub-shells ALLOW subscripts, capitals IGNORE 1s2 seen twice ALLOW 6.021023 particles (atoms, molecules, ions etc.) OR NA particles OR L particles ALLOW Avogadro number in place of NA particles ALLOW Number of atoms in 12 g of 12C DO NOT ALLOW the number of particles in 12g of 12C atoms ALLOW Energy to remove one mole of electrons from one mole of gaseous atoms for three marks IGNORE element ALLOW Energy needed to remove an electron from one mole of gaseous atoms (to form one mole of gaseous 1+ ions) for two marks For third mark: ALLOW ECF if wrong particle is used in second marking point but is described as being gaseous eg molecule instead of atom If no definition, ALLOW one mark for X(g) (cid:198) X+(g) + e OR X(g)e (cid:198) X+(g) ALLOW e for electron IGNORE state symbols on e<br />
F321 Mark Scheme January 2012 Question 3 (d) (i) From F to Ne Answer (ii) From Ne to Na Nuclear charge mark: Ne has (one) more proton OR Nuclear charge increases (cid:57) Same shell or energy level mark: (Outermost) electrons are in the same shell OR energy level OR (Outermost) electrons experience the same shielding (cid:57) Nuclear attraction mark: Greater nuclear attraction (on outermost electrons) OR Outer electrons are attracted more strongly (to the nucleus) (cid:57) Extra shell or energy level mark: Na has (one) more shell(s) OR energy level (cid:57) Shielding mark: (Outermost) electron experiences greater shielding (cid:57) Nuclear attraction mark: Less nuclear attraction (on outermost electrons) OR Outer electrons are attracted less strongly (to nucleus) (cid:57) Total Marks 13 Guidance Use annotations with ticks, crosses, ECF etc for this part ALLOW proton number increases but IGNORE atomic number increases IGNORE nucleus gets bigger IGNORE charge increases ie must be nuclear charge IGNORE effective nuclear charge increases ALLOW sub-shell for shell but IGNORE orbitals ALLOW shielding is similar ALLOW screening for shielding IGNORE Atomic radius decreases (because given in question) OR outermost electrons are closer DO NOT ALLOW distance is the same for second mark ALLOW greater nuclear pull for greater nuclear attraction DO NOT ALLOW greater nuclear charge instead of greater nuclear attraction for the third mark IGNORE pulled closer for pulled more strongly Use annotations with ticks, crosses, ECF etc for this part ALLOW next shell OR new shell ALLOW (outermost) electrons in a higher energy level ALLOW outermost electrons OR shell further from nucleus IGNORE Atomic radius increases (because given in question) DO NOT ALLOW orbitals OR sub-shells ALLOW screening for shielding ALLOW more electron repulsion from inner shells ALLOW less nuclear pull for less nuclear attraction DO NOT ALLOW less nuclear charge for less nuclear attraction for third mark. There must be a clear comparison<br />

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