Ions and Ionic bonds

-Describe the formation of positive ions, known as cations, and negative ions, known as anions

Ions are charged particles formed when atoms lose or gain electrons to achieve stable electronic configuration.

Metal atoms lose electrons to form positively charged ions (cations) .

Eg: A sodium atom has electronic configuration of 2.8.1. To obtain a stable electronic configuration of 2.8, it loses one valence electron to another atom. It becomes a sodium ion with a charge of +1.

Non-metal atoms gain electrons to form negatively charged ions (anions).

Eg: A chlorine atom has electronic configuration of 2.8.7. To obtain a stable electronic configuration of 2.8.8, it gains one valence electron from another atom. It becomes a chloride ion with a charge of -1.

Examples

-Describe the formation of ionic bonds between ions of metallic and non-metallic elements, including the use of dot-and-cross diagrams

Ionic compounds are formed between metallic and non-metallic elements when they react with each other.
 

Eg: Sodium atom will transfer one valence electron to chlorine atom. This will form positively charged sodium ion and negatively charged chloride ion. Both ions will then achieve stable electronic configuration.

Formula of Sodium chloride is NaCl. 

Magnesium oxide
 
Eg Magnesium atom with electronic configuration of 2.8.2 will transfer 2 valence electrons to oxygen atom with electronic configuration of 2.6. This will form positively charged magnesium ion and negatively charged oxide ion. Both ions will then achieve stable electronic configuration of 2.8. Formula of magnesium oxide is MgO..

-State that an ionic bond is a strong electrostatic attraction between oppositely charged ions

-Describe the giant lattice structure of ionic compounds as a regular arrangement of alternating positive and negative ions

Example of lattice structure of sodium chloride:

Oppositely charged sodium and chloride ions form a regular pattern or lattice of alternating positive and negative ions held by strong electrostatic forces of attraction (ionic bonds).

-Describe and explain in terms of structure and bonding the properties of ionic compounds:
(a) high melting points and boiling points

Ionic compounds have high melting and boiling points due giant ionic lattice structure with strong ionic bonds (electrostatic forces of attraction between positively charged ions). Large amount of energy is needed to break these strong bonds.

(b) good electrical conductivity when aqueous or molten and poor when solid

Ionic compounds Conduct electricity in molten and aqueous state due to mobile ions. They do not conduct in solid state due to absence of mobile ions.