IONIC COMPOUNDS

DID YOU KNOW?

Sports drinks consist primarily of water, sugar and salt, with addictives to give a particular taste.

Sports drinks were developed to help football players gain energy & replenish ions lost in perspiration

The characteristics of a product are a direct result of the properties of the substance it contains.

Sports drinks have electrolytes.

WHAT’S A CHEMICAL BOND

The force of attraction holding two atoms or ions together in a compound

Bond is invisible

CHEMICAL COMPOUNDS (TWO TYPES) 1. IONIC COMPOUNDS 2. MOLECULAR COMPOUNDS

Each type has distinctive physical and chemical properties

IONIC COMPOUNDS

Ions- lose or gain electrons to become ions. Ions are either positive or negative charges.

Ionic Bonds- occurs when electrons are completely transferred from one element to another. This results in the formation of a positive ion (the electron donor) and the negative ion (the electron acceptor)

Ionic bonds are usually between a metal (cation) & non-metal (anion)

IONIC COMPOUNDS

Ions in ionic compounds are held together by the electrostatic force between oppositely charged bodies.

Basically it is a bond between a positively charged molecule (cation) and a negatively charged molecule (anion).

Ratio of ions (formula units) 

PROPERTIES OF IONIC COMPOUNDS

Ionic compounds are: Hard and brittle High melting & boiling points Conduct electricity as molten liquid. (not

as solids) Conduct electricity when dissolved in water Examples of ionic compounds – NaCl(salt),

CaCO3 (limestone) and HgS (Cinnabar)

ELECTROLYTE

A compound that dissolves in water to produce a solution that conducts electricity

Example: NaCl dissolved in water = conducts electricity

Sports drinks contain electrolytes, as well as, sugar and flavouring

Electrolytes are important in the body because they help carry electrical impulses throughout the body. As you exercise & sweat, you lose electrolytes

NaCl

NaCl

+-

Before we can understand the formation of ionic compounds we need to know about Lewis diagrams

LEWIS THEORY1. Electrons, esp those with the outermost (valence)

electronic shell play a fundamental role in chemical bonding

2. In some cases, electrons are transferred from one atom to another. Positive & negative ions are formed & attract each other through electrostatic forces called Ionic Bonds

3. In other cases, one or more pairs of electrons are shared between atoms. A bond formed by a sharing of electrons between atoms is called a covalent bond

4. Electrons are transferred or shared in such a way that each atom acquires an especially stable electron configuration. Usually this is a noble gas configuration on with eight outer-shell electrons or an Octet

LEWIS DIAGRAMS Elemental properties &

reactions are determined only by electrons in the outer energy levels. Electrons in completely filled energy levels are ignored when considering properties.

Simplified Bohr diagrams which only consider electrons in outer energy levels are called Lewis Symbols.

LEWIS DIAGRAMS

A Lewis Symbol consists of the element symbol surrounded by "dots" to represent the number of electrons in the outer energy level as represented by a Bohr Diagram.

The number of electrons in the outer energy level is correlated by simply reading the Group number.

Lewis symbols for oxygen, fluorine, and sodium are given in the diagram on the left.

Lewis Symbols for the elements of the second period. Correlate the number of dots with the group number.

LEWIS DIAGRAM

FORMATION OF IONIC COMPOUNDS

Ions- lose or gain electrons to become ions.

Ions are either positive or negatively charged

Lose e= Cation (+) metals Gain e= Anions (-) non metalsNaClNa [Na

]

+ + e

-

Cl + e

[Cl ]-

FORMATION OF IONIC COMPOUNDS

An ionic bond forms when the non-metal atom removes an electron from the metal atom

Electrons are transferred from Sodium (Na) atom to the Chlorine (Cl) atom, forming positive Sodium (Na) & negative Chlorine (Cl)

Na Cl+ [Na ]

+ + [ Cl ]

-

FORMATION OF IONIC COMPOUNDS

Electrostatic Forces is the force that attracts a positively charged objects to a negatively charged one.

This force holds together the charged sodium and chloride ions.

The bond between a positive ion & negative ion is a Ionic Bond

FORMATION OF IONIC COMPOUNDS

Example: Mg + Cl Magnesium atoms lose 2 electrons to form Magnesium

ion, [Mg ], with a complete valence shell. These 2 electrons are taken by two different chlorine

atoms that, in turn, becomes 2 chloride ions, [ Cl ] The resulting compound, magnesium chloride has a

chemical formula of MgCl 2

-

Mg

+ 2 Cl [Mg]

[ Cl ]

[ Cl ]

+2- -

PRACTICE

Draw a Lewis symbols to show the formation of bonds within

1. sodium oxide 2. potassium chloride 3. calcium chloride 4. calcium oxide 5. potassium oxide

Take up practice

STRUCTURE OF IONIC COMPOUNDS

The rigid arrangement of ions is called a Crystal Lattice Structure

Depending on the specific elements involved in the ionic bond, crystal lattices take a variety of forms, but each is regular, repeating pattern.

STRUCTURE OF IONIC COMPOUNDS

This is ultimately results in their ability to crystalize into specific geometric shapes in their solid form.

Form different crystal shapes b/c of different sizes of the ions & the strength with which they attract each other.

STRUCTURE OF IONIC COMPOUNDS

Ionic Compounds Is not made up of one positive ion and one

negative ion Ionic compound is composed of a huge

number of positive & negative ions in a fixed ratio.

Formula Unit the smallest repeating unit in an ionic

crystal

EXPLAINING THE PROPERTIES OF IONIC COMPOUNDS

Ionic Compounds have high melting points because their ions are held together by strong electrostatic forces (ionic bonds)

Ionic compounds are hard because their bonds resist being “stretched”

EXPLAINING THE PROPERTIES OF IONIC COMPOUNDS

Easily cracked & fracture because when an outside force strikes the crystal, the crystal lattice structure is offset. Suddenly, positive charged ions are side by side with other positively charged ions. A repulsive force quickly develops between the like charges and the crystal breaks

EXPLAINING THE PROPERTIES OF IONIC COMPOUNDS

Ionic compounds are electrolytes because when an ionic crystal is placed in water, water molecules surround each ion & separate it from the crystal, The crystal breaks up or dissolves, releasing free-floating ions into the solution. The ions are able to move, & thus to carry electric charges, through the water. This is what happens when electricity passes through a solution.