JPJC 2026 Atomic Structure Revision

© Jurong Pioneer Junior College 1 Topic 1: Atomic Structure JURONG PIONEER JUNIOR COLLEGE Topical Revision for Physical Chemistry (Topic 1: Atomic Structure) FOUNDATION KIT 1 [PJC MYE 2010/P1/Q6] Which atom has three unpaired electrons? A Al B Sc C Cr D Co 2 [AJC Promo 2016/P1/Q2] The electronic configuration of a gold atom, Au, is [Xe] 4f14 5d10 6s1. What is the number of unpaired electrons in the 5d orbitals of the gold ion in AuCl3? A 1 B 2 C 3 D 4 3 [PJC Promo 2013/P1/Q27] Paramagnetic elements are elements which are attracted by an externally applied magnetic field. In general, paramagnetism is observed for elements which have one or more unpaired electrons. Which of the following elements could be paramagnetic? 1 Manganese 2 Titanium 3 Zinc A 1, 2 and 3 are correct B 1 and 2 are correct C 2 and 3 are correct D 1 only is correct 4 [PJC MYE 2012/P1/Q16] A species of Z has the following electronic configuration. What could Z be? 1 Cl+ ion 2 S atom 3 Ar2─ ion A 1, 2 and 3 are correct B 1 and 2 are correct C 1 and 3 are correct D 2 and 3 are correct 5 [PJC MYE 2013/P1/Q7] Which of the following species is deflected to the least extent in an electric field? A +2Mg2412 B +3Al2713 C −216 8O D −232 16S

© Jurong Pioneer Junior College 2 Topic 1: Atomic Structure 6 [PJC MYE 2010/P1/Q7] In an experiment, a sample of gadolinium element was vaporised, ionised and passed through an electric field. Analysis of the deflection occurring at the electric field region revealed the following data for a beam of 157Gd+. What would be the angle of deflection for a sample of 87Sr2+? A 0.6 o B 3.6 o C 7.2 o D 16.5 o 7 [AJC Promo 2016/P1/Q3] modified Gaseous particle U has an atomic number n and a charge of +1. Gaseous particle V has an atomic number of (n + 1) and is isoelectronic with U. Which of the following statements is always true? 1 V has a smaller radius than U. 2 V is deflected less than U when passed through an electric field as it has a larger mass 3 V has more neutrons than U. A 1, 2 and 3 are correct B 1 and 2 are correct C 2 and 3 are correct D 1 only is correct 8 [PJC MYE 2011/P1/Q5] The use of the Data Booklet is relevant to this question. The successive ionisation energies, in kJ mol-1 of element X are given below. 870 1800 3000 3600 5800 7000 13200 What is X? A 33As B 40Zr C 52Te D 53I

© Jurong Pioneer Junior College 3 Topic 1: Atomic Structure 9 [PJC MYE 2012/P1/Q6] The table gives the successive ionisation energies (IE) for two elements, F and G. IE / kJ mol–1 1st 2nd 3rd 4th 5th 6th 7th 8th F 1090 2350 4610 6220 37800 47000 - - G 1251 2298 3822 5158 6542 9362 11018 33604 What could be the formula of the compound that is formed when F reacts with G? A FG B F2G3 C FG4 D F4G 10 [PJC MYE 2013/P1/Q6] The successive ionisation energies, in kJ mol−1, of an element R are given below. 1020 1900 2910 4960 6200 21300 25400 Which Group does R belong to? A 13 B 14 C 15 D 6 11 [PJC Promo 2010/P1/Q6] Which of the following electronic configurations represents an atom of an element with the highest first ionisation energy? A 1s2 2s2 2p3 B 1s2 2s2 2p4 C 1s2 2s2 2p6 3s1 D 1s2 2s2 2p6 3s2 3p3 12 [PJC Promo 2013/P1/Q5] modified Why is the first ionisation energy of oxygen lower than that of nitrogen? A Oxygen is more electronegative than phosphorus. B Oxygen forms anions more readily. C The electron to be lost in oxygen is paired with another electron which experiences inter- electronic repulsion. D The electron to be lost in oxygen is from a 2p orbital which is higher in energy.

© Jurong Pioneer Junior College 4 Topic 1: Atomic Structure 13 [AJC Promo 2016/P1/Q1] Use of the Data Booklet is relevant to this question. On 9th October 2006, a team of scientists from America and Russia reported the discovery of element 118, the heaviest element yet discovered. The atoms have a mass number of 294. The element has provisionally been named Ununoctium and given the symbol Uuo. Which statement about this element and its compound is correct? 1 It has 176 neutrons. 2 It forms a square planar tetroxide UuoO4. 3 It has a higher first ionisation energy than that of 86Rn. 4 It has two more occupied electron shells than a Cs+ ion. A 1 only B 3 only C 1 and 4 only D 2 and 3 only 14 [CJC Promo 2016/P1/Q4] modified The orbitals illustrated below are of the same scale but not necessarily placed in any order. Y2− has all of these orbitals completely filled. Which of the following statements is false? A The electronic configuration of Y is 1s2 2s2 2p4. B In an isolated atom of element Y, the orbitals (A), (B) and (C) are completely filled with electrons while orbitals (D) and (E) are half-filled. C Element Y has a lower first ionisation energy than Na. D Na+ has a smaller ionic radius than Y2- x z y (C) x z y (D) x z y (E) x z y x z y (B) (C) (A)

© Jurong Pioneer Junior College 5 Topic 1: Atomic Structure 15 [ACJC Prelim 2020/ P2/ Q1a] The Periodic Table currently used is derived from that proposed in 1869 by Mendeleev who had noticed patterns in the physical and chemical properties of the elements he had studied. (a) (i) The atomic radius of Period 3 elements decreases from Na to Cl. Explain why this is so. (ii) Write the electronic configurations of the sodium atom and its ion. Na 1s2………………………………… Na+ 1s2………………………………… (iii) Explain the difference in the radius of the sodium atom and the radius of its ion, Na+. 16 [TPJC Prelim 2011/ P2/ Q4a] After aluminium, iron is the most abundant metal in Earth’s crust. It is a typical transition element and plays a crucial role in the biological system. Give the electronic configurations of Fe and Fe2+. 17 [PJC MYE 2010/P2/Q3] The graph below shows a plot of successive ionisation energies for an element, A, in Period 2. (a) Identify element A, explaining your answer. (b) (i) Define what is meant by first ionisation energy of an element. (ii) State and explain the general trend of the first ionisation energies across period 2. (iii) Element B has 1 more proton than element A and has a lower first ionisation energy than A. Explain why this is so. log10 ionisation energies No. of electrons removed

© Jurong Pioneer Junior College 6 Topic 1: Atomic Structure 18 [PJC MYE 2012/P2/Q2] (a) Describe and explain briefly the general trend in ionisation energy down a group. (b) (i) The following graph below shows the second ionisation energies of eight elements with consecutive proton number Which of the above elements, A to H, is sulfur? Explain your answer (ii) Explain why the second ionization energy of B is lower than that of A. (iii) Explain why the second ionization energy of D is similar to that of E. 19 [EJC Prelim 2020/ P2/ Q1d] Table 1.2 shows the successive ionisation energies of an element A. Table 1.2 ionisation energies / kJ mol−1 1st 2nd 3rd 4th 5th 6th 7th 8th 9th 10th element A 945 1794 2735 4839 6056 11690 14180 17370 20550 23830 (a) (i) Explain why the successive ionisation energies of an element always increase. (ii) Is element A likely to be from the same group as nitrogen? Explain your answer clearly. (iii) State and explain how the first ionisation energy of element A will compare to that of the element to its right in the periodic table. 20 [YJC Prelim 2013/ P2/ Q2a] Elements J, K, and L are consecutive elements in period 3 of the Periodic Table. The first eight ionisation energies, I.E., of eleme