Lesson 2: Ionic Bonds, Ionic Compounds

Weak Pull in Ionic Compunds

Comparably low EN, and low number of Valence electrons 

 

Strong Pull In Ionic Compound

 Comparably high EN, and high number of  Valence electrons 

Electronegativity

the ability of an atom in a chemical bond to attract shared electrons towards itself

With great electronegativity difference between a metals and nonmetals electron(s) is/are transferred from the

less electronegative atom to the more electronegative atom.  

 

This forms oppositely charged ions that attract each other 

oppositely charged ions that attract each other result in

the formation of an ionic bond, hence an ionic compound 

The ionic compound has different

chemical and physical properties than the elements it is made from 

Ionic compound formation is not limited to electron transfer…  It is the

attraction between the cation and the anion in the same medium 

Ionic bonding = 

electrostatic attraction between cations and anions

Electrostatic

Force that pulls oppositely charged particles 

 ionic bonding can be called

Chemical bonding that results from the electrostatic attraction between the oppositely charged ions, cations (positively charged ion) and anions (negatively charged ion)

Both atoms in an ionic bond aim to have

complete valence shell – Octet Rule 

Lewis Dot Structure and Ionic Bonds 

Electron-dot structures helps us to describe and illustrate the formation of chemic 

al bonds. 

Chem symbol in the middle

valence electron around, order doesnt matter

helium has to have 2 paried together

Electrical forces in an ionic compound produce 

unique physical structures 

In an ionic compound, large numbers of positive ions and negative ions exist together in a

 fixed ratio

The ions are packed into a regular repeating pattern called 

lattice 

The strong attractions among the positive ions and the negative ions in an ionic compound result in the formation of a 

crystal lattice, which is three-dimensional geometric arrangement of particles 

crystal lattice

three-dimensional geometric arrangement of particles 

Ionic compound is composed of positive and negative ions combined in a

fixed ratio so that the numbers of positive and negative charges are equal 

And every positive ion is surrounded with

negative ion and every negative ion is surrounded with positive ion 

Ionic compounds generally have common physical properties: 

• High melting and boiling points 

• Hard, rigid and brittle 

• Conduct electricity ONLY when molten or dissolved in water 

Melting point, boiling point, and hardness are  physical properties.  and are determined by

the strength of electrical forces between particles in matter.  

Ionic bonds are relatively strong, so ionic crystals require a lot of

energy to break. Thus, the crystals have high melting and boiling points. 

Strong electrostatic attraction between the cations and the anions resulting in

Ionic lattice (the regular arrangement of positively and negatively charged ions) 

 

Ionic Bonds Are hard, rigid and brittle solids due to

strong attraction between electric charges that hold the ions in place 

Crystals break when a

 

force strong enough to overcome these attractive forces is applied - Similar charged ions repel each other 

 

Ionic Compounds Conduct electricity once

molten (liquid state) at high temperature or dissolved in water (solution) 

The ability of a material to conduct electricity depends on the

 availability of freely moving charged particles.  

In ionic compounds in solution or a liquid state, ions are

free to move. Thus, these compounds conduct electricity. 

In a solid ionic compounds, ions are locked in

position by strong attractive forces. Thus, ionic solids usually do not conduct electricity 

Moving Ions

Conduct electricity once dissolved in water   (But NOT IN SOLID STATE!!) 

 

electrolyte 

 

Ionic compound whose aqueous solution conducts an electric current

Energy in an Ionic Bond - Lattice Energy is the energy released when

 one mole of an ionic crystalline compound is formed from gaseous ions - This process is exothermic 

A process either 

absorb or release energy 

 endothermic  

Process that absorb energy 

exothermic 

Process that release energy  

Greater lattice energy reflects

stronger force of attraction between the oppositely charged ions 

Lattice energy is usually written as

negative because energy is released 

Also, if energy is released when ionic bonds are formed, then

energy must be supplied to break these bonds. 

Factors affecting Lattice Energy:  

Higher ionic charge, stronger attraction, higher energy 

Ionic bonds formed from ions with larger positive or negative charges also have  

greater lattice energy

Smaller ionic size/radius, stronger attraction, higher energy 

Smaller ions form compounds with more closely spaced ionic charges, so they have stronger attractions and greater lattice energies)

Why do these factors affect lattice energy

• The electrostatic force of attraction between opposite charges increases  

• As the distance between the charges decreases/ionic size decreases 

• And as the charges of the ions increases