Presentation on theme: "Ch. 6 Chemical Bonding A Chemical Bond occurs when valence electrons are lost, gained, transferred or shared between two or more atoms."— Presentation transcript:
1 Ch. 6 Chemical BondingA Chemical Bond occurs when valence electrons are lost, gained, transferred or shared between two or more atoms.
2 The Octet Rule Atoms tend to gain, lose, or share electrons until they have eight valence electrons.This is called a “Stable Octet.”
3 Why Do Atoms form a Bond? To form a state of lower potential energy. Bonded atoms require less energyTo become more stable.A Stable Octet of 8 electrons resembles the Nobel Gases.
4 The Three types of Bonds Ionic Bond – Transfer of electrons from a cation to an anion.
5 The Three types of Bonds Covalent Bond Sharing of electrons so that all atoms involved maintain a Stable octet.
6 Three types of BondsMetallic Bond Cations attracted to other Cations by a sea of electrons surrounding all of the positive ions.Sea of electrons
7 Identifying the BondWhen Metals bond to Non-Metals they will form an Ionic BondWhen Non-Metals bond to other Non-Metals they will form a Covalent BondWhen Metals bond to other Metals they will form a Metallic Bond
8 Lewis Dot DiagramsLewis symbols show the valence electrons as dots arranged around the atomic symbol.hydrogen:sodium:chlorine:HNaCl· ·
9 Using Lewis Dot Diagrams for Ionic compounds and Covalent molecules Formation of sodium chloride:Cl· ·Na+Cl· ·Na+Formation of hydrogen chloride:Cl· ·Cl· ·HH+When filling up valence shells make sure all non-metals finish with a stable octet. If possible all elements should finish with an octet.
10 Ex. NaCl and MgO not “ClNa” or “OMG” Basic Formula WritingWhen writing a formula the most metallic element is written first.(leftmost on the P.table)Ex. NaCl and MgO not “ClNa” or “OMG”Subscripts are to be used to represent the number of elements or ions needed to make all species maintain a octet.Ex. H2O or AlBr3(A subscript of 1 is understood and is not written.)
11 Bond Determination H + F Ca + Cl Al + O * Cu + N K + P N + Br As + S Using e-dot diagrams determine the formulas for the following.Metal to Non-Metal IonicNon-Metal to Non-Metal CovalentH + FCa + ClAl + O* Cu + NK + PN + BrAs + SIonic CovalentHFCaCl2Al2O3Cu3N or Cu3N2K3PNBr3As2S3When writing the formula of a compound or molecule the more metallic element is always written 1st ( furthest to the left)
12 Determining Formulas The Criss-Cross Method A short cut to formula writing can be accomplished using the oxidation or charge of ions to determine the chemical formulas of compounds.ExamplesNa+1 + O-2 Ca+2 + P-3 C+4 + O-2 Na2OCa3P2C2O4 reduced to CO2