Chapter 7 : Ionic Compounds And MetalsSection 2 : Ionic Bonds And Ionic Compounds

Objectives Describing the formation of ionic bond

Explaining: compound formation and charge

True or False Table salt (sodium chloride ) conducts electricity .

Ionic Bonds And Ionic CompoundsOppositely charged ions attract each

other, forming electrically neutral ionic compounds

Formation of an Ionic Bond Ionic bond : The electrostatic force that

holds oppositely charged particles together in an ionic compound

Compounds that contain ionic bonds are Ionic compounds

If ionic bonds occur between metals and the (oxygen) , oxides form. Most other ionic compounds are called salts.

Binary ionic compoundsIonic Compounds that contain only two

different elementsFor Example : NaCl contains two different

elements, which are sodium and chlorine.

Compound formation and charge  

Example (calcium fluoride )Calcium needs to lose two electrons to attain

the stable configuration of argon.Fluorine must gain one electron to attain the

stable configuration of neon

(1)(2+) + (2)(1–) = 0

7- sodium loses one electron to form 1+ ion and nitrogen needs to gain 3 electrons forming 3- ionThe ions attract forming Na3N

Summarize the charges on each ion in the following ionic compoundsMgO , NaF , SrCl2

Mg 2+ , O2- , Na + , F - ,Sr 2+ , Cl -

Physical properties of ionic compoundsMelting point, boiling point, and hardness are physical

properties of matter that depend on how strongly the particles that make up the matter are attracted to one another

the ability of a material to conduct electricity depends on the availability of freely moving charged particles.

In the solid state, the ions in an ionic compound are locked into fixed positions by strong attractive forces. As a result, ionic solids do not conduct electricity.

but when an ionic solid melts to become a liquid or is dissolved in solution. The ions are now free to move and conduct an electric current.

Physical properties

Electrolyte :An ionic compound whose aqueous solution conducts the electricity

Ionic crystals have high melting points and high boiling points , Why?

Because ionic bonds are relatively strong, ionic crystals require a large amount of energy to be broken apart

What makes the crystal cracks ?

the crystal cracks or breaks apart, as shown in Figure 9. The crystal breaks apart because the applied force repositions the like-charged ions next to each other; the resulting repulsive force breaks apart the crystal.

Energy and the Ionic Bond

ExothermicEndothermic

During every chemical reaction, energy is either absorbed or released.

If energy is absorbed during a chemical reaction, the reaction is endothermic. If energy is released, it is exothermic

The formation of ionic compounds from positive ions and negative ions is always Exothermic

Properties of Ionic Compounds the ionic bonds produce unique physical

structures, unlike those of other compounds A crystal lattice is a three-dimensional

geometric arrangement of particleslattice energy :the energy required to

separate 1 mol of the ions of an ionic compound

In a crystal lattice, each positive ion is surrounded by negative ions, and each negative ion is surrounded by positive ions.

crystal lattice is a three-dimensional geometric arrangement of particles In a crystal lattice, each positive ion is surrounded by negative The greater the lattice energy, the stronger

the force of attraction. Lattice energy is related to the size of the

ions bonded. Because the electrostatic force of attraction

between opposite charges increases as the distance between the charges decreases

1- Smaller ions produce stronger interionic attractions and greater lattice energies.• For example : • The lattice energy of a lithium compound

is greater than that of a potassium compound containing the same anion because the lithium ion is smaller than the potassium ion.

2- The value of lattice energy is also affected by the charge of the ion.• The ionic bond formed from the

attraction of ions with larger positive or negative charges generally has a greater lattice energy.

Size and charge & lattice energy

So : MgO is four times greater than NaF