ionic bonds and ionic compounds
TRANSCRIPT
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