13028 13 The table below shows the first ionisation energies and the electronegativity values of the elements in the second period. Element Li Be B C N O F Ne First ionisation energy /kJ mol-1 520 900 800 1090 1400 1310 1680 2086 Electronegativity 1.0 1.5 2.0 2.5 3.0 3.5 4.0 (a) (i) Write an equation which represents the first ionisation energy of lithium. [2] (ii) State and explain the general trend in the first ionisation energy across the second period. Identify and explain any exceptions to this general trend. In this question you will be assessed on using your written communication skills including the use of specialist terms. [6] 13028 [Turn over (b) (i) State what is meant by electronegativity. [2] (ii) Explain the change in electronegativity across the second period. [2] 13028 (c) Fluorine forms an ionic compound with lithium, lithium fluoride (LiF), and a covalent compound with oxygen, oxygen difluoride (OF2). (i) Using electronegativity, explain why lithium fluoride is ionic. [1] (ii) Draw a dot and cross diagram for a molecule of oxygen difluoride using outer electrons only. [2] (iii) Show the polarity of an oxygen–fluorine bond, using partial charges. O—F [1] (iv) State the shape of the oxygen difluoride molecule. [1] 13028 BLANK PAGE DO NOT WRITE ON THIS PAGE (Questions continue overleaf) [Turn over