Topic: 9.2

The elements phosphorus, sulfur and chlorine are in Period 3 of the Periodic Table. Table 1.1 shows some properties of the elements P to Cl . The first ionisation energy of S is not shown.

(a) (i) Complete Table 1.1 to show the number of electrons in the 3p subshell and the total number of unpaired electrons in an atom of P, S and Cl .
(ii) Construct an equation to represent the first ionisation energy of P.
(iii) Three possible values for the first ionisation energy of S are given.
1000 kJ/mol,  1160 kJ/mol, 1320 kJ/mol
Circle the correct value.
Explain your choice by comparing your chosen value to those of P and Cl .

(b) \(P^{3–}\), \(S^{2–}\) and \(Cl^–\) have the same number of electrons.
(i) Give the full electronic configuration of P3–.

(ii) State the trend in ionic radius shown by \(P^{3–}\), \(S^{2–}\) and \(Cl^–\). Explain your answer.
(c) A student does three tests on separate samples of NaCl (aq). Complete Table 1.2 with the observations the student makes in each test.

(d) POCl₃ shows similar chemical properties to PCl₅. POCl₃ has a melting point of 1°C and a boiling point of 106°C. POCl₃ reacts vigorously with water, forming misty fumes and an acidic solution.
(i) Explain how the information in (d) suggests the structure and bonding of POCl₃ is simple covalent.
(ii) Construct an equation for the reaction of POCl₃ with water.
POCl₃ + ………………….. \(to\) ………………………
(iii)POCl₃ contains a double covalent bond between P and O. Complete the dot-and-cross diagram, in Fig. 1.1, to show the bonding in POCl₃. Show outer shell electrons only.

(e) POCl₃(g) forms when PCl₃(g) reacts with O₂(g).
\(2PCl_3(g) + O_2(g) \to 2POCl_3(g)\)
Table 1.3 gives some relevant data

(i) Define enthalpy change of formation, \(\Delta H_f\).
(ii) Calculate the bond energy of P=O in POCl₃ using the data in Table 1.3. Show your working