5.2 Formation of Ionic Bonds

Formation of cation and anion
■ Formation of cation and anion

	►	An atom is neutral because it has an equal number of protons and electrons.
	►	An ion formed when an atom donates or accepts one or more electrons.

■ Formation of cation

	►
	►	When an atom donates electrons, it becomes positively charged as there are more protons than electrons in it.
	►	A positively charged ion or cation is obtained.
	►	M → Mn+ + ne

■ Formation of anion

	►
	►	When an atom accepts electrons, it becomes negatively charged as there are more electrons than protons in it.
	►	A negatively charged ion or anion is obtained
	►	A + ne → An-

Formation of ionic bonds
■ Formation of ionic bonds

	►	Electrons are transferred from a metal to a non-metal.
	►	The metal donates its valence electron(s) to attain the noble gas stability. Positive ions (cation) are formed.
	►	The non-metal received the electron(s) to attain the noble gas stability. Negative ion (anion) are formed.
	►	The positive and negative ions are held together by strong electrostatic forces of attraction.
	►	This strong electrostatic forces of attraction between ions of opposite charges is known as ionic bond.
	►	The animation below shows the formation of sodium chloride (NaCl), magnesium oxide (MgO), and sodium oxide (NaO2).

■ This video contains information on the formation of ionic bonds.

Laboratory Activity 5.2.1: Preparation of Ionic Compounds

Determining the ionic compound formulae
■ Formulae of an ionic compound.

	►	Metal atoms will release their valence electrons to achieve the stable electron arrangement as in the inert gases.
	►	Non-metal atoms will accept electrons in order to achieve the stable electron arrangement of the inert gases.
	►	For cations Mb+ and anions Xa-, the formula of an ionic compound formed between them is written as MaNb.
	►	The total positive charge of the cation must be equal to the negative charge of the anion in an ionic compound.
	►	Hence, the formula of an ionic compound formed between them can also be derived as follows : aMb+ + bXa- → MaNb

✍ Worked-example 5.2(a)
Complete the following table to show the written ionic compound formulae.
Solution 

Atom	Proton number	Electron arrangement	Ion formula	Atom	Proton number	Electron arrangement	Ion formula
A	3	2.1	A+	V	9	2.7	V-
B	11	2.8.1	B+	W	8	2.6	W2-
C	12	2.8.2	C2+	X	17	2.8.7	X-
D	20	2.8.8.2	D2+	Y	9	2.7	Y-
E	19	2.8.8.1	E+	Z	17	2.8.7	Z-

← 5.1 Formation of Compounds

5.3 Formation of Covalent Bonds →

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