JPJC 2026 Atomic Structure Tutorial

2026 JC1 H2 Chemistry (9476) 1 Topic 1: Atomic Structure JURONG PIONEER JUNIOR COLLEGE 2026 JC1 H2 Chemistry (9476) Core Idea 1 – Matter Topic 1: Atomic Structure Tutorial Level 1 – Self–Check Questions Sub−atomic particles, Atomic Orbitals & Electronic Configuration 1 For the negatively charged ion −31 2 15P , determine the number of (a) protons (f) orbitals containing electrons (b) neutrons (g) completely filled orbitals (c) electrons (h) partially filled orbitals (d) energy levels (quantum shells) containing electrons (i) unpaired electrons (e) energy sub−levels (sub-shells) containing electrons (j) valence electrons 2 Complete the following table. Species Electronic configuration 35Br 6C+ 15P3− 25Mn2+ 29Cu+ 24Cr2+ 3 An unknown element X forms X3− ions which are isoelectronic with Ar. (a) Write the electronic configuration of element X. (b) Show the electronic configuration of an atom of X using an energy level diagram. 4 The colours observed in street lamps are due to the effect of ionisation of gaseous atoms inside the lamps. The sodium−vapour street lamps, which contain neon gas and a small amount of solid sodium in the lamps, appear red (due to the ionisation of neon gas) when they first come on and eventually become yellow when the sodium starts ionising. (a) Write equations to represent the first ionisation energy of neon and sodium. (b) Hence, with the aid of appropriate data from the Data Booklet, account for the order of the colours observed.

2026 JC1 H2 Chemistry (9476) 2 Topic 1: Atomic Structure 5 The table below gives the ionisation energies (in kJ mol−1) of lithium, sodium and potassium. 1st IE 2nd IE 3rd IE 4th IE Lithium 526 7310 11800 − Sodium 502 4560 6920 9540 Potassium 425 3060 4440 5880 (a) Explain why the first ionisation energies decrease from lithium to potassium. (b) Explain why the successive ionisation energies of each element increases. (c) Why is there no value given for the 4th ionisation energy of lithium? Level 2 – Application Questions Behaviour of charged particles in electric field 6 (a) When separate beams of 63Cu2+ and 127I− are passed through the electric field, as shown in the diagram below, they behave differently. A beam of neutrons has already been drawn. (i) Sketch and label on the diagram how the beams of 63Cu2+ and 127I− are affected by the electric field. (ii) Given that the angle of deflection of the Cu 2+ beam is +7.0°, calculate the angle of deflection of the I− beam, correct to 1 decimal place. (b) Plasma is a gaseous mixture in which the atoms have been completely stripped of their electrons, leaving bare nuclei. When passed between two plates carrying a certain electric charge, 1H and 4He nuclei are deflected as follows. Suggest, with reasoning, (i) the polarity (+ or −) of plate A, (ii) why 1H is deflected twice as much as 4He, (iii) the angle of deflection of 2H nuclei and 3He nuclei. Source neutrons Source B + A 1H 4He 2° 4° + -

2026 JC1 H2 Chemistry (9476) 3 Topic 1: Atomic Structure Electronic configuration 7 (a) Write the electronic configurations for Fe2+ and Fe3+ ions. (b) Explain why the ionic radius of Fe3+ is smaller than that of Fe2+. Atomic Orbitals 8 [N2018/P2/Q1(part)] Describe one similarity and one difference between • a 1s and a 2s orbital, • a 2s and a 2p orbital. Ionisation Energies 9 [N2014/P2/Q4] The graph below can be used to plot the first ionisation energy of the element gallium to strontium. Four of these elements have been plotted. (a) Use your knowledge of the variation in first ionisation energy of the elements of Period 3 (Na to Ar) to estimate and plot, on the graph below, the first ionisation energies of the other four elements: As, Se, Kr and Rb. (b) Justify your predictions in (a), by explaining why the first ionisation energy of each element you have plotted is higher / lower / similar compared to the element to its left on the graph.

2026 JC1 H2 Chemistry (9476) 4 Topic 1: Atomic Structure 10 The following table shows the ionisation energies (in kJ mol−1) of five elements lettered A, B, C, D and E. Element 1st IE 2nd IE 3rd IE 4th IE A 500 4600 6900 9500 B 740 1500 7700 10500 C 630 1600 3000 4800 D 900 1800 14800 21000 E 580 1800 2700 11600 (a) Which element is most likely to form an ion with a charge of +1? Explain. (b) Which two elements are in the same Group of the Periodic Table and to which Group do they belong to? (c) To which Group of the Periodic Table would element E most likely to be in? Explain your answer. (d) Which element would require the least energy to convert one mole of gaseous a toms into ions with a +2 charge? 11 The graph shows the energy required to remove ten electrons from an atom of Y. (a) Which group of the Periodic Table does element Y belong? (b) Explain why Y cannot be an element belonging to Period 2. (c) Explain why the ionisation energies increase as the electrons are being removed. (d) Name an element that could be Y and write its electronic configuration. lg (IE) 1 2 3 4 5 6 7 8 9 10 no. of electrons removed

2026 JC1 H2 Chemistry (9476) 5 Topic 1: Atomic Structure 12 [N2022 A-level Paper 2 Q1 and Q2 (modified)] Table 1.1 lists the number of protons, neutrons and electrons in seven different particles. Each particle may be an atom, an anion or a cation. Table 1.1 particle number of protons number of neutrons number of electrons A 18 22 18 B 18 22 17 C 20 20 20 D 20 20 18 E 17 20 18 F 17 18 17 G 17 20 17 (a) Use the information in T able 1.1 to identify • the two particles which are a pair of isotopes of the same element. • the cation with the same electronic configuration as an atom of argon. • the pair of atoms of different elements with the same nucleon number. (b) In (i) and (ii) deduce which particle is larger. Explain each answer. (i) C and D (ii) D and E Fig. 2.1 shows successive ionization energies of the Period 4 element selenium, Se. (c) State the number of electron pairs in an atom of Se. (d) Complete Fig. 2.1 by plotting approximate values for the 2 nd successive ionisation energy and the 6th successive ionisation energy of Se (e) All elements are each assigned a value of electronegativity on the Pauling scale. Francium has the lowest electronegativity value of 0.7 and fluorine has the highest electronegativity value of 4.0. Oxygen has an electronegativity value of 3.5 on the Pauling scale. Suggest the electronegativity value for Se by comparison with that given for oxygen. Explain your answer.

2026 JC1 H2 Chemistry (9476) 6 Topic 1: Atomic Structure 13 [N2003/P1/Q4] In 1999 Russian chemists claimed to be the first to identify atoms of a new element of proton number 114. This was produced by bombarding atoms of plutonium, Pu, with atoms of an isotope of a Group 2 element, X. The reaction that took place is given below.   ( ) 289244 1 94 0 114Pu new element 3 neutrons n+ → +X What is X? [Hint: Sum of atomic numbers and sum of mass numbers are conserved ( i.e. constant).] A Mg B Ca C Sr D Ba 14 [N2010/P1/Q3] The radioactive isotope, Po, was said to be the agent that poisoned the former Russian security agent, Alexander Litvinenko, in London in November 2006. Po 210 84 decays to give an element, X, and emits a high energy −particle (which is a helium nucleus He 4 2 ). No other particle is produced. −particles cause irreparable damage to the tissues of internal organs. Po 210 84 → He 4 2 + X Which row in the table correctly describes the nuclear make u