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IBChemistryHLExam QuestionsModels of the Particulate Nature of MatterElectronic Configurations

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First exams 2025

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Electronic Configurations (HL IB Chemistry)

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Electronic Configurations

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Electronic Configurations

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11 mark

Using the Aufbau Principle and Hund’s rule, deduce which element below has the greatest number of unpaired electrons in its ground state.

  • Z = 13

  • Z = 14

  • Z = 15

  • Z = 16

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21 mark

Which electron transition would emit radiation of the longest wavelength?

2-1-e-q10-mcqs-ib-chemistry

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    31 mark

    Why is the second ionisation energy of magnesium higher than the first ionisation energy?

    • Less shielding

    • Ionic radius increases

    • Nuclear charge is increasing

    • Greater attraction between positive nucleus and outer electron

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    4
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    Which is true about the emission spectrum of hydrogen in the visible region?

    • The lines converge at longer wavelengths

    • The lines converge at higher frequency

    • The lines come from transitions between n=∞ and n=1

    • The lines are regularly spaced

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    5
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    The frequency of the point of convergence on a hydrogen emission spectrum is 32.883 x 1014 s-1.

    What is the ionisation energy for one atom of hydrogen?

    (h = 6.63 x 10-34 J s)

    • 2.18 x 10-18 J

    • 2.02 x 10-49 J

    • J

    • 4.96 x 1045 J

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    6
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    The first five ionisation energies of an element are shown below.

    What element could this ionisation energy graph belong to?

    successive-ionisation-energy

    • N

    • P

    • Al

    • Na

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    7
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    Which are correct explanation(s) for the increase in ionisation energy across a period?

    I. Nuclear charge increases

    II. Atomic radius decreases

    III. Shielding remains constant

    • I and II only

    • I and III only

    • I and III only

    • I,II and III

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    8
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    Which spectrum belongs to hydrogen?

    eARGWkkX_hydrogen-spectrum

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      11 mark

      There are six unpaired electrons in atoms of element Z. What could element Z be?

      • sulfur

      • iron

      • carbon

      • chromium

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      21 mark

      The diagram shows three orbitals labelled 1, 2 and 3. 

      2-1-m-q5-mcqs-ib-chemistry

      What is the correct label for each orbital?

      • px, py and pz

      • s, pz and py

      • s, px and pz

      • s, px and py

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      31 mark

      What is the electronic configuration of an ion with a single negative charge and atomic number 17?

      • 1s2 2s2 2p6 3s1 3p6

      • 1s2 2s2 2p6 3s2 3p6

      • 1s2 2s2 2p6 3s1 3p5

      • 1s2 2s2 2p6 3s2 3p5

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      41 mark

      What is the correct sequence for the orbitals shown in an atom of vanadium in order of decreasing energy?

      • 3s 3p 4s 3d

      • 4s 3d 3s 3p

      • 4s 3d 3p 3s

      • 3d 4s 3p 3s

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      51 mark

      The second ionisation energy of magnesium is 1451 kJ mol-1. 

      Which equation correctly represents this statement?

      • Mg+(g) → Mg2+(g) + e-          ΔHӨ = -1451 kJ mol-1

      • Mg+(g) → Mg2+(g) + e-          ΔHӨ = +1451 kJ mol-1

      • Mg(g) → Mg2+(g) + 2e-         ΔHӨ  = +1451 kJ mol-1

      • Mg(g) → Mg+(g) + e-            ΔHӨ = -1451 kJ mol-1

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      61 mark

      X, Y and Z  are consecutive elements in the third Period of the Periodic Table. Element Y has the highest first ionisation energy and also the lowest melting point of these three elements. 

      What could be the identities of X, Y and Z?

      • silicon, phosphorus, sulfur 

      • sodium, magnesium, aluminium

      • aluminium, silicon, phosphorus

      • magnesium, aluminium, silicon

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      71 mark

      An element in the d block of the periodic table forms a +4 ion and has the electron configuration of [Ar] 3d1.

      What is the identity of the element?

      • Chromium

      • Copper

      • Vanadium

      • Silicon

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      81 mark

      Deduce the correct information about the element tin, Sn (Z = 50)

        Number of occupied
      main energy levels      		 Number of electrons in the
      highest main energy level

      A

      4

      4

      B

      4

      14

      C

      5

      4

      D

      5

      14

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        91 mark

        Which of the following calculations gives the correct calculation to find the energy, in kJ, for a photon of blue light given the wavelength ƛ = 550 nm.

        h = 6.626 x 10−34J s; c =  2.988 x 108 m s-1

        • 3.60 x 10-19

        • 3.60 x 10-31

        • 3.60 x 10-22

        • 6.63 x 10-37

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        101 mark

        Successive ionisation energies for an element, Y, are shown in the table below.

        Electrons removed

        1st

        2nd

        3rd

        4th

        5th
        Ionisation energy / kJ mol-1

        736

        1450

        7740

        10500

        13600

        What is the most likely formula for the ion of Y?

        • Y+

        • Y2+

        • Y3+

        • Y4+

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        111 mark

        Values for the successive ionisation energies for an unknown element are given in the table below.

        First ionisation energy / kJ mol-1

        Second ionisation energy / kJ mol-1

        Third ionisation energy / kJ mol-1

        Fourth ionisation energy / kJ mol-1

        420

        3600

        4400

        5900

        In which group of the periodic table would the unknown element be found?

        • 1

        • 2

        • 13

        • 14

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        121 mark

        The graph shows the first ionisation energies of some consecutive elements

        x-and-y-ionisation-energiesWhich statement is correct?

        • Y is in group 13

        • Y is in group 10

        • X is in group 15

        • X is in group 18

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        131 mark

        Which transition on the diagram corresponds to the ionisation of hydrogen in the ground state?

        ionisation-of-ground-state-hydrogen

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          11 mark

          Element X is in period 2 and has the first seven ionisation energies in kJ mol-1 as shown.

              1300    

              3380    

              5330    

              7460    

              11 010    

              13 320    

              71 200    

          What is the electronic configuration of element X?

          • 1s2 2s2 2p4

          • 1s2 2s2 2p2

          • 1s2 2s2 2p3

          • 1s2 2s2 2p6

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          21 mark

          For the successive ionisation energies of oxygen, where would the highest jump be expected to occur?

          • second ionisation energy

          • first ionisation energy

          • seventh ionisation energy

          • sixth ionisation energy

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          31 mark

          Which species produces a half-filled set of p orbitals on losing an electron?

          • Li+

          • F

          • N

          • N-

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          41 mark

          Which statement explains why electrons pair up in orbitals before occupying an orbital of a higher energy level?

          • the energy from repulsion is greater than the jump to a higher orbital

          • electrons occupy higher energy orbitals before lower energy orbitals

          • electrons in lower orbitals have higher energies

          • the energy from repulsion is less than the jump to a higher orbital

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          51 mark

          Which equation is correct for the third ionization energy for the element nitrogen?

          • N+(g) → N4+(g)  + 3e-

          • N2+(g) → N3+(g)  + e-

          • N(g) → N3+(g)  + 3e-

          • N3+(g) → N4+(g)  + e-

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          61 mark

          A line emission spectrum occurs when

          • electrons release energy as they move from high to low energy levels

          • electrons release energy as they move from low to high energy levels

          • electrons absorb energy as they move from high to low energy levels

          • electrons absorb energy as they move from low to high energy levels

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          71 mark

          A spectral line that would be found in the visible spectrum of the hydrogen emission spectrum would be

          • n1 → n2

          • n2 → n3

          • n3 → n2

          • n3 → n∞

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          8
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          Which statement is true about the spectra shown? hydrogen-spectrum-hl

          • All the lines in R have the same energy

          • Q and S could represent line emission spectra

          • Only S could represent a line emission spectrum for hydrogen

          • P indicates the element has 4 pairs of electrons at different energy levels 

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          9
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          The energy absorbed at the limit of convergence for helium is 19.6 x 10-18 J per atom.

          Which calculation would be used to calculate the wavelength, in m, for this electron transition?

          (c = 3.00 x 108 ms-1, h = 6.63 x 10-34 Js)

          • 8.89 x 1024

          • 1.01 x 10-8

          • 4.33 x 10-59

          • 2.31 x 1058

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          10
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          The first ionisation energies (in kJ mol-1) of five successive elements are:

          2081, 496, 738, 578, 787

          What could these elements be?

          • First five elements in a period

          • Second to the sixth elements in a period

          • Last four elements of one period and the first one of the next period

          • Last element of one period and the first four elements of the next period

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          11
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          A period 3 element forms an oxide M2O3.

          Which represents the first four successive ionisation energies of M?

            Ionisation energy / kJmol-1
            First Second Third Fourth
          A. 496 4560 6940 9540
          B. 578 1820 2740 11600
          C. 1012 1907 2914 4964
          D. 736 1450 7740 10500

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            12
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            Between which ionisation energies of silicon will there be the greatest difference?

            • Between the second and fourth ionisation energies

            • Between the first and third ionisation energies

            • Between the fourth and fifth ionisation energies

            • Between the fifth and sixth ionisation energies

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