Two unknown elements, Q and R

CHEMISTRY · Multi-part · A Level · Chemistry · Periodicity and periodic trends · Periodicity and periodic trends

Problem

Two unknown elements, Q and R, are known to be in the same period of the periodic table. • Successive ionization energy data for element Q are: IE1=801 kJ mol−1\mathrm{IE}_1 = 801\,\text{kJ}\,\text{mol}^{-1} IE2=2427 kJ mol−1\mathrm{IE}_2 = 2427\,\text{kJ}\,\text{mol}^{-1} IE3=3658 kJ mol−1\mathrm{IE}_3 = 3658\,\text{kJ}\,\text{mol}^{-1} IE4=25020 kJ mol−1\mathrm{IE}_4 = 25020\,\text{kJ}\,\text{mol}^{-1} • The electronegativity of element R is 3.04 (Pauling). (a) Determine the most probable group number for element Q. Show how the data support your conclusion. (b) Using periodic-trend reasoning, decide whether element Q or element R has the larger atomic radius. Explain fully. (c) Identify specific elements (by chemical symbol) that Q and R are most likely to be. State any assumptions you make. (d) A binary compound is formed from elements Q and R. Write its empirical formula and describe the dominant type of chemical bonding expected. Justify your answer by linking it to the periodic-trend information provided.

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