Ch. 6 Chemical Bonding valence A Chemical Bond occurs when valence electrons are lost, gained,...
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Transcript of Ch. 6 Chemical Bonding valence A Chemical Bond occurs when valence electrons are lost, gained,...
Ch. 6 Chemical Bonding
A Chemical Bond occurs when valencevalence electrons are lost, gained, transferred or shared between two or more atoms.
The Octet RuleAtoms tend to gain, lose, or share electrons
until they have eight valence electrons.
This is called a “Stable Octet.”
Why Do Atoms form a Why Do Atoms form a Bond?Bond?
To form a state of lower potential energyTo form a state of lower potential energy. Bonded atoms require less energy
To become more stableTo become more stable. A Stable Octet of 8 electrons resembles the Nobel Gases.
The Three types of The Three types of BondsBonds
Ionic Bond –
Transfer of electrons from a
cation to an anion.
The Three types of BondsThe Three types of Bonds
Covalent Bond Sharing of electrons so that all atoms involved
maintain a Stable octet.
Three types of BondsThree types of Bonds
Metallic Bond Cations attracted to other Cations
by a sea of electrons
surrounding all of the positive ions.
Sea of electrons
Identifying the Bond
When MetalsMetals bond to Non-MetalsNon-Metals they will form an Ionic Bond
When Non-MetalsNon-Metals bond to other Non-MetalsNon-Metals they will form a
Covalent Bond
When MetalsMetals bond to other MetalsMetals they will form a Metallic Bond
Lewis Dot Diagrams
Lewis symbols show the valence electrons as dots arranged around the atomic symbol.
hydrogen:
sodium:
chlorine:
Na
H
Cl
Using Lewis Dot Diagrams for Ionic compounds and Covalent
molecules• Formation of sodium chloride:
• Formation of hydrogen chloride:
When filling up valence shells make sure all non-metals finish with a
stable octet. If possible all elements should finish with an octet.
Na + Na+ [ ]Cl
Cl
H + Cl
Cl
H
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”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. Ex. HH22O or AlBrO or AlBr33
(A subscript of 1 is understood and is not (A subscript of 1 is understood and is not written.)written.)
Bond Determination Using e-dot diagrams determine the formulas for the following.Using e-dot diagrams determine the formulas for the following.
Metal to Non-Metal Metal to Non-Metal Ionic Ionic Non-Metal to Non-Metal Non-Metal to Non-Metal Covalent Covalent
Ionic IonicIonicIonicIonic CovalentCovalent
HFCaCl2Al2O3
Cu3N or Cu3N2
K3PNBr3
As2S3
1. H + F2. Ca + Cl 3. Al + O4. * Cu + N5. K + P6. N + Br7. As + S
When writing the formula of a compound or molecule the more metallic element is always
written 1st ( furthest to the left)
Determining FormulasThe 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.
• Examples Na+1 + O-2
Ca+2 + P-3
C+4 + O-2
Na2O
Ca3P2
C2O4 reduced to CO2