My Share Learning Content: 5.2 Formation of Ionic Bonds

Saturday, 17 January 2015

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 → A^n-

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.

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 M^b+ and anions X^a-, the formula of an ionic compound formed between them is written as M_aN_b.
	►	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 : aM^b+ + bX^a- → M_aN_b

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