Sample of Essay Question

Form 4 Chapter 5:

1		Table 11 shows the proton number of atoms P, Q and R.
		Element P Q R Proton number 8 12 17
	a)	Based on electron arrangement, explain the formation of chemical bond between
	i)	element P and element P                                                      [5 marks ]
	ii)	element Q and element R                                                     [7 marks ]
	b)	Gas P reacts with element Q to produce a white solid.
	i)	Write a chemical equation for the reaction between gas P and element Q.
	ii)	State three physical properties of the white solid.              [ 4 marks] ]
	c)	What is the position of element Q in the Periodic Table of the elements? Explain how you obtain your answer.                                  [ 4 marks ]

Suggested Answer:

1	a)i	1.   Two atoms of P combine through covalent bond.                            2.   Each atom of P needs two more electrons to achieve octet electron arrangement. 3.   Each atom of P contributes two electrons to each other for sharing.               4.   Two atoms of P share two pairs of electrons. 5.   A double covalent bond is formed.
	ii)	1.    Atom Q and atom R combine through ionic bond 2.    To achieve octet electron arrangement,                                          3.    atom Q with 6 valence electrons loses two electrons to form Q2+ ion              4.    Two atom R, each atom with 7 valence electrons gain one electron to form R- ion.                                                                       5.   Q2+ ion and R- ion are attracted to each other by strong electrostatic force.1   Diagram
	b)i	2Q   +   P2      -->       2QP
	ii)	Have high melting point Usually soluble in water                                                                            Conduct electricity in the molten state or aqueous solution.
	c)	1.    Element Q is located in Group 2                                                       2.    because it has two valence electrons                                            3.    Element Q is located in Period 3                                                       4.    because it has three shells occupied with electrons