11852 15 The third Period in the Periodic Table from sodium to argon displays a number of periodic trends. (a) State and explain the general trend in first ionisation energy across Period three. [3] (b) (i) Write an equation, including state symbols, for the first ionisation energy of phosphorus. [2] (ii) Explain why the first ionisation energy of phosphorus is higher than that of sulfur. [2] 11852 [Turn over (c) The graph below shows the melting points of the elements in the third Period. Na Mg Al Si P S Cl Ar 1800 1600 1400 1200 1000 800 600 400 200 0 melting point/K With reference to the structure and bonding of the elements, explain the change in melting point from silicon to argon. In this question you will be assessed on your written communication skills including the use of specialist scientific terms. [6]