Number of neutrons. what name is given to these different atoms of gallium? Isotopes (1)

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Bernice Griffith
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1 1. (a) Complete the following table Atom Number of protons Number of neutrons Number of electrons Ir Mo pne Ir Mo (b) The element gallium consists of two types of atom of relative mass 69.0 and 71.0 respectively. The percentage abundance of the atoms of relative mass 69.0 is 60.2 (c) (d) (i) Calculate the relative atom mass of gallium. ( ) + ( ) = 69.8 or what name is given to these different atoms of gallium? Isotopes Define the term second ionisation energy. Write an equation, using he element potassium, to show this change. The energy required to remove 1 mole of electrons from (1 mole of) gaseous + 2g+ unipositive ions K (g ) K ( ), + e The first seven ionisation energies (kj mol-1) for two elements A and B in the same period of the Periodic Table are: (i) Element A B Explain the relative magnitudes of the first and second ionisation energies of element B. More energy required to remove 1 mole of electrons from a positively charged particle than from a neutral atom Explain the relative magnitude of the first ionisation energy for elements A and B. A = Group 5 and B = Group 3 (3) Hence A has greater nuclear charge so more energy required to overcome attraction of nucleus for electron (4) (Total 11 marks) NT Exampro 1

2 2. Complete the following table p n e Ir Mo The element gallium consists of two types of atom of relative mass 69.0 and 71.0 respectively. The percentage abundance of the atoms of relative mass 69.0 is 60.2 (i) Calculate the relative atom mass of gallium. ( ) + ( ) = 69.8 or what name is given to these different atoms of gallium? Isotopes 4. Define the term isotope. atoms with same number of protons but different number of neutrons OR same element with different number of neutrons NOT same atom with different number of neutrons accept same atomic number with different mass number 5. From the position of radium in the periodic Table, predict the following: (a) the formula of radium carbonate; (b) the equation of the thermal decomposition of solid radium carbonate; RaCO 3 (s) RaO(s) + CO 2 (g) balanced equation state symbols (only if correct species) (c) how the decomposition temperature required in (d) would compare with tat required for magnesium carbonate. (temperature) higher (for Ra) 6. (a) Define the terms: (i) atomic number; number of protons in one atom (iii) mass number; number of protons + neutrons in one atom relative atomic mass mean mass of atom relative to 12 C = 12 if mean or average missing (½) only (Total 4 marks) NT Exampro 2

3 (b) In 1919 F. W. Aston, using an early form of the mass spectrometer, showed that neon exists as a mixture of isotopes. The mass spectrum is shown below; determine the relative atomic mass of neon. relative abundance m/e (0.1 22) + (0.9 20) = 20.2 ignore any units (c) (i) Define the second ionisation energy of fluorine. H (½) per mole (½) F+ (g) F2+(g) + e (OK to use X instead of F) OE if in words (heat) energy change (½) per mol(½) species (½) states (½) (all marks conditional on correct species ie F+ F2+) Sketch a graph on the axes below to show the successive ionisation energies of fluorine. Give reasons for the shape of the line you draw. 7. Define the terms: (a) atomic number; number of protons in one atom (4) (Total 11 marks) NT Exampro 3

4 (b) (c) mass number; number of protons + neutrons in one atom relative atomic mass mean mass of atom relative to 12 C = 12 if mean or average missing (½) only (Total 3 marks) 8. (i) Give the electronic configuration of an atom of the isotope of calcium, Ca. 1s2 2s2 2p6 3s2 3p64s2 (iii) Give the names and numbers of each type of particle present in a nucleus of this isotope. 25 neutrons 20 protons State one reason why the information in (a)(i) is usually more useful to chemists than that in (a). reactions/chemical properties depend on electron structure/outermost orbital 9. (a) (i) electrons 16.. protons 16.neutrons 16. All correct 1 they are isotopes The word isotope or some derivative is essential 1 (iii) S2 / sulphide(2 ) ion / sulphur 2 ion / sulphur with two extra electrons but not just S or sulphur 1 (b) (i) X(g) + e- X-(g) (S(g) + e- S-(g)) X-(g) + e- X2- (g) (S-(g) + e- S2-(g)) can have Z in place of X2- but not Z2- Penalize omission of state symbol (g) only once. 2 adding a negative onto a negative requires energy to overcome repulsion or second electron repelled by negative charge Not second electron repelled by first 1 (c) (ßdecay from) Y produces only one isotope( 35Cl) natural sample contains two isotopes (35 and 37) 2 (Total 4 marks) [8] NT Exampro 4

5 10. (a) (i) Atomic number: number of protons ( in the nucleus) Mass number: [Total/sum of the)numbers of protons plus/and neutrons 2 Na+ or 11 23Na+ or a sodium ion 1 (b) (i) ( 79Br81Br )+ or ( 79 Br 81 Br )+ 1 Some working or justification 50:50 or equivalent 2 e.g. Because the two peaks at 158 and 162 are the same height the relative abundance of each must be 50% (c) The heat /energy/ enthalpy change/ released per mole of electrons for addition to 1mol of gaseous(bromine) atoms Br(g) + e Br (g) 3 The word gaseous may be omitted provided the state symbol is present on both sides of the equation / vice versa (d) (i) The heat /energy/ enthalpy change/needed per mol of electrons for removal from 1mol of gaseous(neon) atoms The equation is not asked for but can be used to score the second mark above. 2 Ne(g) e Ne+(g) (The first ionisation energy increases as) the nuclear charge increases (Inner shell) shielding remains the same (as nuclear charge increases)/ electrons removed from same energy level/shell 2 (iii) there is less inner shell shielding in Ne Although there is an increase in the nuclear charge from Ne to Ar OR atomic radius for Ne is smaller than for Ar/ the outer (2p) electron in Ne is closer to the nucleus than the (3p) electron in Ar (a) (i) electron configuration or 3d64s2 or 4s2 or number of outer electrons 1 26 protons, 26 electrons, 30 neutrons all 3 any 2 2 (iii) atoms (of same element) with same number of protons or same atomic number 1 different number of neutrons or mass number 1 (b) (i) A ionisation not vaporisation 1 B acceleration 1 C deflection 1 D detection 1 [15] NT Exampro 5

6 (5.8 54) + ( ) + (2.2 57) + ( ) = [11] 12. (a) (i) 2s22p63s23p (b) (i) Energy/heat/enthalpy change/released per 1 mole of gaseous atoms for the gain of 1 electron 3 (Negative) electron and negative ion/anion (both) negative Repulsion occurs (a) (i) Number of protons + number of neutrons 1 (weighted) average / mean mass of one atom relative to one twelfth the mass of carbon-1 2 (atom) / on a scale in which 12C = 12 2 (iii) atoms with same atomic no/ same no of protons/ same element but different numbers of neutrons / mass number 2 (b) ( ) + ( ) + ( ) (a) Proton + 1 Electron 1/1800 1/2000 or negligible Neutron charge 0 / no charge 3 Correct p n e in both C and H Notes there are 4 H Correct summation i.e 10p, 10e, 6n 3 If no or inadequate working 1 mark for 10 p & 10 e 1 mark for 6 n. (c) (1s2) 2s22p63s23p5 1 (d) 37Cl+ charge(stand alone) 2 37 if incorrect number of protons / mass number shown max 1 for charge (e) (i) S(g) + e S (g) species and charges state symbols in part (i) and equations 2 [7] [7] NT Exampro 6

7 (f) S(g) S+(g) + e or S(g) e S+(g) 1 Species and charge No need to show negative charge on electron. If use X in place of S penalise once only Chlorine nucleus has greater charge / is more positive / has greater number of protons outer electron / electron being removed, is in same shell / has same shielding 2 [14] 15. (a) (i) 2Li + 2H 2 O 2LiOH + H 2 (g) species balance 2 Any two from: Solid floats / moves around on surface bubbles evolved / fizzes liquid remains colourless 2 (b) Protons 3 Neutrons 4 Electrons 2 3 (c) Relative atomic mass ( ) + ( ) = (must be three s.f.) 2 (d) Dip Pt / nichrome wire in solid and place in hot/blue flame Na salt gives yellow colour Li salt give deep / magenta red / crimson colour (a) (i) Weighted average (mass) of 1 atom on a scale in which 1 atom of 12C = 12 units / compared to 1/12 atom of 12C 2 Number of protons plus / and neutrons or nucleons in a nucleus / an atom. 1 (iii) Atoms of same atomic number / same proton number which differ in the number of neutrons (in the nucleus) 2 (b) (i) Concept of high energy electron collision: Electron bombardment / gun / acceleration / fired knocks off electron / equation showing electron being knocked off 2 Positive, +, S+ 1 (iii) Voltage differential across plates / charged plates [plural] / electrostatic field / electric field 1 [12] NT Exampro 7

8 (c) [ ] / 100 = = NOT 32 or (d) 1s²2s²2p63s²3p4 1 [12] NT Exampro 8

2. (a) (i) Atomic number: number of protons ( in the nucleus) (1) Mass number: [Total/sum of the)numbers of protons plus/and neutrons (1) 2

2. (a) (i) Atomic number: number of protons ( in the nucleus) (1) Mass number: [Total/sum of the)numbers of protons plus/and neutrons (1) 2 1. (a) 36.5/23 = 1.59 25.4/32 =0.79 38.1/16 =2.38 (1) 1.59/0.79 = 2.01 0.79/0.79 =1.00 2.38/0.79 =3.01 (1) Na 2 SO 3 (1) 3 (b) (i) 25.0 1/1000 = 0.025 2.5 10 2 (1) 1 (ii) 300/24 000(1) =0.0125 1.25 10