Comparison of Properties Ionic Compounds Covalent Compounds Metals Chemical Bonding Comparison of Properties Ionic Compounds Covalent Compounds Metals

What is a chemical bond? An attractive force that holds two atoms together Can form by The attraction of positive ion to a negative ion or The attraction of the positive nucleus of one atom and the negative electrons of another atom

Bond the interaction between two or more atoms that allows them to form a substance different from the independent atoms. involves the outer (valence) electrons of the atoms. These electrons are transferred from one atom to another or shared between them.

Chemical Bond Energy Considerations A chemical bond forms when it is energetically favorable when the energy of the bonded atoms is less than the energies of the separated atoms. Al + I2 https://www.youtube.com/watch?v=XBPqSuIN-3E

Bonding Chemical compounds are formed by the joining of two or more atoms. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms. The bound state implies a net attractive force between the atoms ... a chemical bond.

Energy Changes in Bonding When bonds are formed, energy is released. Demonstrations: Formation of an Ionic Compound: Mg + O2 Formation of a Molecular Compound: S + O2

Breaking Bonds In order to break bonds energy must be added, usually in the form of heat, light, or electricity. Demonstration: Electrolysis of water Demo: Decomposition of Nitrogen Triiodide http://www.youtube.com/watch?v=z5vsQ8sPgX4

Three Types of Bonding Ionic Metallic Covalent

Chemical Bonds In chemical bonds, atoms can either transfer or share their valence electrons.

When atoms transfer electrons Ionic Bonds When one or more atoms lose electrons and other atoms gain them in order to produce a noble gas electron configuration, the bond is called an ionic bond.

Metals Nonmetals

Ionic Bonds Part 1 Part 2 Part 3 http://www.youtube.com/watch?v=Qf07-8Jhhpc Part 2 http://www.youtube.com/watch?v=5EwmedLuRmw Part 3 http://www.youtube.com/watch?v=RkZNYuSho0M

Ion Formation All of the elements in Group I have one electron in their outermost energy level. All of these elements can lose that one valence electron. These atoms become cations with a positive one charge.

Elements in Group II have two electrons in their outermost energy level. So, when these elements lose electrons, they lose two electrons and take on a positive two charge.

Anions Nonmetals tend to gain electrons. The halogens - fluorine, chlorine, bromine, and iodine - have a strong attraction for electrons. Their outermost energy levels are almost full. There is only room for one more electron in the outer energy levels for each of those atoms. Consequently, the elements fluorine, chlorine, bromine, and iodine will gain one electron, and become anions with a negative one charge. Oxygen, sulfur, and the other elements in that family will gain two electrons. In the next group over, nitrogen, phosphorus and arsenic can take on three electrons.

+1 +2 +3 -3 -2 -1

Ionic Nomenclature Naming Ionic Compounds Video of the Process http://www.youtube.com/watch?v=URc75hoKGLY

Ionic Compounds Made of cations and anions Metals and nonmetals The electrons lost by the cation are gained by the anion The cation and anions surround each other Smallest ratio of ions in an ionic compound is a FORMULA UNIT.

K+1 Ca+2 Cations Positive ions Formed by losing electrons More protons than electrons usually Metals K+1 Has lost one electron Ca+2 Has lost two electrons

F-1 O-2 Anion A negative ion Has gained electrons Non metals Charge is written as a super script on the right. F-1 Has gained one electron O-2 Has gained two electrons

Formula Unit The smallest whole number ratio of atoms in an ionic compound. Ions surround each other so you can’t say which is hooked to which

Name these Na+1 Ca+2 Al+3 Fe+3 Fe+2 Pb+2 Li+1

Write Formulas for these Potassium ion Magnesium ion Copper (II) ion Chromium (VI) ion Barium ion Mercury (II) ion

Naming Anions Change the element ending to – ide F-1 Fluorine

Name these Cl-1 N-3 Br-1 O-2 Ga+3

Write these Sulfide ion iodide ion phosphide ion Strontium ion

Write these Sulfide ion iodide ion phosphide ion Strontium ion

Binary Ionic Compounds Binary Compounds 2 elements. a cation and an anion. To write the names just name the two ions. Easy with Representative elements Groups 1, 2, 13 NaCl = Na+ Cl- = sodium chloride MgBr2 = Mg+2 Br- = magnesium bromide

Naming Binary Ionic Compounds Write the names of the following KCl Na3N CrN Sc3P2 PbO PbO2 Na2Se

Writing Formulas Given the name write the formula The charges have to add up to zero Write down each ion with charges Make the charges equal by adding subscripts Put polyatomic ions in parentheses if you need more than one of them

Writing Formulas Example Write the formula for calcium chloride.

Molecular (Covalent) Substances

Covalent Bonds involve the sharing of a pair of valence electrons by two atoms Such bonds lead to stable molecules if they share electrons in such a way as to create a noble gas configuration for each atom

Covalent bonding can be visualized with the aid of a Lewis Structure

Naming Covalent Molecules Nonmetal nonmetal Use the prefix to indicate the number of atoms present

Prefix nonmetal1 prefix nonmetal2

Metals and Metallic Bonding Typical Properties of Metals Malleable Ductile Good Conductors of Heat and Electricity Generally high melting and boiling points

Metallic Bonds The properties of metals suggest that their atoms possess strong bonds yet the ease of conduction of heat and electricity suggest that electrons can move freely in all directions in a metal The general observations give rise to a picture of "positive ions in a sea of electrons" to describe metallic bonding.

Metallic Bonding Electron Sea Model Explained by the Electron Sea Model the atoms in a metallic solid contribute their valence electrons to form a “sea” of electrons that surrounds metallic cations. delocalized electrons are not held by any specific atom and can move easily throughout the solid. A metallic bond is the attraction between these electrons and the metallic cation.

Metallic Bonding the Electron Sea Model The more delocalized electrons the stronger the bond