IB Chemistry S3.1: The periodic table worked solutions

A main-group atom occupies period 4, group 2. Which statement follows directly?(A) It has two occupied shells and four valence electrons. (B) It has four occupied shells and two valence electrons. (C) Its atomic number is four. (D) Its outer electrons occupy a p sublevel.

A materials catalogue lists aluminium, silicon, nickel and neon. Which entry describes silicon correctly?(A) Metal, s-block (B) Metalloid, p-block (C) Non-metal, d-block (D) Transition element, p-block

A neutral calcium atom forms \mathrm{Ca}^{2+}. Which change explains the smaller size of the ion?(A) The nucleus loses two protons. (B) Two neutrons are removed from the nucleus. (C) The atom gains two electrons and repulsion decreases. (D) Its outermost occupied shell is removed, leaving electrons closer to the same nucleus.

Which statement describes a negative first electron affinity?(A) A gaseous atom gains an electron and releases energy. (B) A gaseous atom loses an electron and releases energy. (C) A gaseous positive ion gains an electron and absorbs energy. (D) A bonded atom attracts a shared electron pair more strongly.

Which prediction is correct for dilute aqueous iodine added to aqueous lithium chloride?(A) Chlorine forms because iodine has more occupied electron shells. (B) Lithium metal forms because lithium is in group 1. (C) No halogen displacement occurs because iodine gains electrons less readily than chlorine. (D) Hydrogen forms because every group 1 substance reacts with water.

A sulfur oxide has one sulfur atom for every three oxygen atoms. Which paired description is correct?(A) Sulfur state -6; acidic oxide. (B) Sulfur state +3; acidic oxide. (C) Sulfur state +6; basic oxide. (D) Sulfur state +6; acidic oxide.

Which observation would best distinguish a typical first-row transition metal from a group 2 metal?(A) The solid conducts electricity. (B) The element forms at least one positive ion. (C) Its compounds exhibit several metal oxidation states. (D) The element can react with an acid.

A complex solution absorbs mainly green light. Using the six-colour wheel in the data booklet, which colour is expected to dominate the transmitted light?(A) Green (B) Yellow (C) Orange (D) Red

For a covalent bond between unlike atoms, define electronegativity and state whether it has an energy unit.

A schematic first-ionization-energy trace follows three consecutive elements A, B and C. B is a noble-gas maximum, followed by a sharp fall at C. The horizontal axis is proton number.(a) Give the group of C and explain the fall. [2]

HL: a model complex absorbs at 620\,\mathrm{nm}. Use c=3.00\times10^8\,\mathrm{m\,s^{-1}}.(a) Calculate the absorbed frequency. [2] (b) Would absorption at 530 nm require a larger or smaller d-energy gap? [1]

Element X lies in period 4 and group 16. Only atoms with atomic numbers up to 36 are considered.(a) Identify X and write its condensed electron configuration. [2] (b) Explain how the configuration supports the period and group numbers. [2] (c) Name one other element expected to have similar chemical properties. [1]

The following species are considered: \mathrm{O}^{2-}, \mathrm{F}^{-}, \mathrm{Na}^{+} and neutral \mathrm{Na}.(a) State the electron count for each of the three ions. [1] (b) Order the three ions by increasing radius and justify the order. [3] (c) Explain why the sodium atom is larger than its cation. [2]

An inventory contains \mathrm{CaH_2}, \mathrm{BaO_2}, \mathrm{H_2SO_4} and elemental \mathrm{S_8}.(a) Determine hydrogen in calcium hydride and oxygen in barium peroxide. [2] (b) Calculate the sulfur oxidation state in sulfuric acid. [1] (c) State the sulfur oxidation state in the elemental sample and explain its value. [2]

The data booklet lists I_1(\mathrm{Be})=900, I_1(\mathrm{B})=801, I_1(\mathrm{N})=1402 and I_1(\mathrm{O})=1314\,\mathrm{kJ\,mol^{-1}}.(a) Explain the boron–beryllium reversal using the electron removed from each atom. [2] (b) Explain the oxygen–nitrogen reversal in terms of orbital occupancy. [2] (c) State the general first-ionization trend across period 2 and the reason these results do not invalidate it. [2]

Compare neutral Li/Na down group 1 and Na/Cl across period 3.(a) Explain which of Li and Na has the larger atomic radius. [2] (b) Explain which of Na and Cl has the higher first ionization energy. [2] (c) State the direction of change in atomic radius and electronegativity from Na towards Cl. [2]

Separate water samples receive sodium metal or magnesium oxide in a demonstration.(a) Write the sodium reaction, including states, and name the gas. [2] (b) Give one visible observation from the sodium demonstration. [1] (c) Write the magnesium oxide hydration equation and explain why complete dissolution should not be assumed. [2]

HL: use Zn [\mathrm{Ar}]3d^{10}4s^2, Cu [\mathrm{Ar}]3d^{10}4s^1 and Ni [\mathrm{Ar}]3d^84s^2. Restrict colour predictions to the simple d–d model.(a) Explain why Cu qualifies as a transition element while Zn does not. [2] (b) Compare the d occupancies of \mathrm{Cu^+} and \mathrm{Ni^{2+}}, and identify the ion that can show visible d–d absorption in a suitable ligand field. [2]

Dilute aqueous bromine is added separately to potassium iodide and potassium chloride. Compare group trends.(a) Identify the halide solution in which displacement occurs. [1] (b) Write the net ionic displacement equation and identify the oxidizing species. [2] (c) Explain why the reactivity directions down groups 1 and 17 differ. [2]

A fuel sample contains sulfur as well as carbon. A treatment plant oxidises sulfur completely to sulfur dioxide. Its exhaust then contacts calcium oxide, which captures carbon dioxide as a solid carbonate. Treat the capture reaction as complete for the calculation.(a) Write the sulfur oxidation equation. [1] (b)(i) State an environmental consequence of sulfur dioxide emission. [1] (b)(ii) Write a balanced model equation for sulfur dioxide reacting with water to form sulfurous acid, \mathrm{H_2SO_3}. [1] (c) Write the reaction between calcium oxide and carbon dioxide. [1] (d) Determine the mass of pure calcium oxide needed to capture 22.0\,\mathrm{kg} of carbon dioxide. Use molar masses 56.08 and 44.01\,\mathrm{g\,mol^{-1}}, respectively. [2] (e) Explain why carbon dioxide capture alone does not remove the sulfur-related concern. [1]

An illustrative transition-element record gives the energy cost of each successive removal from gaseous species. Each entry is the cost of that removal alone, per mole, not a cumulative total. These values are not an actual element identification dataset.

Electron removed: 2 / 3 / 4; cost / \mathrm{kJ\,mol^{-1}}: 2110 / 3620 / 9870. (a) Calculate the increase in energy cost from the second to the third removal, and from the third to the fourth removal. [2] (b) Explain how the record can support variable oxidation states +2 and +3, and why it suggests a greater energy cost for reaching +4. [2] (c) Evaluate the claim that these costs alone prove that every compound with the element in state +2 is more stable than one with it in state +3. [2]

Two hypothetical complexes of the same metal ion at the same oxidation state, L and M, are measured at equal concentration in the same cuvette. Their spectra each have one dominant visible band. The table lists absorbances at selected wavelengths.

\begin{array}{c|ccc}\lambda/\mathrm{nm}&450&580&660\\\hline A_L&0.06&0.72&0.09\\A_M&0.81&0.08&0.04\end{array}(a) Select the listed wavelength that provides the greatest sensitivity for measuring the concentration of L. [1] (b) Deduce the main observed colours of L and M using the booklet wheel. [2] (c) Explain why ligand identity can account for different absorption bands even though the metal and oxidation state are unchanged. [2] (d) Name one measurement condition that must remain constant when comparing the two absorbances. [1]

A hypothetical pair of metallic solids X and Y has the same packing geometry. Supplied values: X, molar mass 24.0\,\mathrm{g\,mol^{-1}} and density 1.50\,\mathrm{g\,cm^{-3}}; Y, 60.0\,\mathrm{g\,mol^{-1}} and 3.00\,\mathrm{g\,cm^{-3}}. Use V_m=M/\rho and, only under this packing assumption, r_Y/r_X=(V_{m,Y}/V_{m,X})^{1/3}.(a) Calculate both molar volumes. [2] (b) Estimate the radius ratio and the percentage by which Y is larger. [2] (c) A student claims that the denser solid must have smaller atoms. Evaluate the claim using the calculation and identify one limitation of the radius model. [2]

S3.1 + S1.4 + S1.5. A 0.460\,\mathrm{g} sodium sample reacts completely with excess water. Use M(\mathrm{Na})=22.99\,\mathrm{g\,mol^{-1}} and a supplied gas molar volume 24.0\,\mathrm{dm^3\,mol^{-1}} at the collection conditions.(a) Write the balanced equation with states and predict the solution character. [2] (b) Calculate the volume of dry hydrogen collected, in \mathrm{cm^3}. [3] (c) Explain why equal moles of potassium would usually react more vigorously under comparable conditions. [1]

S3.1 + R3.1 + S1.4. A pure 0.800\,\mathrm{g} MgO sample treats 50.0\,\mathrm{cm^3} of 0.600\,\mathrm{mol\,dm^{-3}} HCl. Use M(\mathrm{MgO})=40.31\,\mathrm{g\,mol^{-1}} and assume complete reaction wherever acid remains.(a) Classify MgO and write its net ionic reaction with acid. [2] (b) Identify the limiting reagent and calculate the mass of MgO left. [3] (c) Explain why a low solubility in water would not make MgO a neutral oxide. [1]

HL: S3.1 + S1.3 + R3.4. A simplified ligand replacement is \ce{[Cu(H2O)6]^{2+} + 4Cl^- <=> [CuCl4]^{2-} + 6H2O}. A model sample has dominant absorption at 600 nm. Use h=6.63\times10^{-34}\,\mathrm{J\,s} and c=3.00\times10^8\,\mathrm{m\,s^{-1}}.(a) Deduce both copper oxidation states and decide whether replacement is redox. [2] (b) Calculate the absorbed photon energy. [2] (c) Explain how ligand replacement can shift the absorption wavelength without changing the metal oxidation state. [2]

S3.1 + R3.2 + S1.4. A 10.0\,\mathrm{cm^3} bromine-water sample is mixed with excess aqueous iodide. The liberated iodine consumes 15.0\,\mathrm{cm^3} of 0.0200\,\mathrm{mol\,dm^{-3}} thiosulfate. Use the supplied reaction \ce{I2 + 2S2O3^{2-} -> 2I^- + S4O6^{2-}}. Assume complete reactions.(a) Write the net ionic reaction that liberates iodine and identify the oxidant. [2] (b) Calculate the original bromine concentration in \mathrm{mol\,dm^{-3}}. [3] (c) Explain why iodine added to aqueous chloride would not liberate chlorine. [1]