C. Goodman, Doral Academy Charter High School, 2011-2013
1. What is a chemical bond? 2. Why do atoms bond? 3. How can a compound s structure be described and modeled?
Chemical bond Bond length Bond angle Chemical structure
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Chemical structure: the arrangement of atoms in a compound Bond length Bond angle
average distance between the nuclei of two bonded atoms
the angle formed by two bonds to the same atom..\..\..\..\physicial Science Resource Disk\Powerpoints\FILES\CH06\75121.html
Ball-and-stick model Structural formulas Space-filling models
1. Network solids covalent bonds 1. High melting/boiling points 2. Very strong 3. Example: quartz
1. Network solids ionic bonds 1. High melting/boiling points 2. Brittle 3. Example: table salt
1. Strong bonds between atoms, weak bonds between molecules 2. Low melting/boiling points 3. Often are liquid or gas at room temperature. 4. Example: water
Crystallization of ionic solutions
1. Contrast ionic, covalent and metallic bonds. 2. How does the type of chemical bond affect the physical properties of a compound?
Ionic bond Covalent bond Metallic bond Molecule Ionic compound
Bonding occurs so atoms become more stable Stability = full valence (8 electrons)
Covalent Share electron pairs to complete valences Ionic Transfer electrons to complete valence for anion, remove extra electron(s) from cation This creates ions Ions attract each other 6e- 6e- 6e- 6e- 8e- 8e- 6e- 6e-
Group of atoms that are held together by covalent bonds
Nonmetal + nonmetal In bonding, metalloids are considered nonmetals Halogens, carbon, oxygen, etc.
A compound composed of positive and negative ions that are attracted (opposites attract)
Metal + nonmetal (cation + anion) Electrons are somewhat moveable, when the compounds are in solutions (conduct electricity) Electrical conductivity of ionic solutions
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Metals + metals Closely packed cations within a sea of electrons Cations can slide around easily if pulled = malleability/ductility Valence electrons of metals drift from one part of the metal to another = conductivity (of heat and electricity)
Electrons can flow freely throughout the metal Good electrical conductors Cations can slide past each other easily Ductile Malleable
Compound Element 1 Element 2 Bond type HCl H: Cl: H2S KBr FeO2 Gold SiO2
1. How do chemical formulas represent a compound? 2. How are ionic compounds named? 3. How are covalent compounds named?
Chemical formula Molecular compound Molecular formula
Chemical Formula Indicates the relative # s of atoms of each kind in a chemical compound by using atomic symbols and numerical subscripts Molecular Compound A chemical compound whose simplest units are molecules Molecular Formula Shows the types and numbers of atoms combined in a single molecule of a molecular compound
Chemical symbols represent the elements in a compound Subscripts represent the number of the element in the compound Examples H2O CO2 Al2O3
1. Cations Element s name + ion Al 3+ is? 2. Anions Drop ending of elements name, add ide Cl - is?
Element symbol N nitrogen C carbon S sulfur Se Selenium O oxygen P phosphorus Cl chlorine F fluorine H hydrogen Br bromine I iodine Name
Example: Aluminum and oxygen 1. Write the name of the cation 2. Append the name of the anion Aluminum Aluminum oxide
Chemical formula Name K 2 O MgI 2 AlCl 3 CaBr 2 Na 3 N LiF Ba 3 P 2 Cs 2 S SrF 2 NaCl
1. Put the ions next to each other, cation first 2. Criss-cross charges to subscripts 3. You re done! Example: Aluminum and oxygen Al 3+ O 2- Notes: a. If need be, reduce the subscripts to the lowest whole number ratio. b. Do not write 1 as a subscript it is understood Al 2 O 3
Cation Anion Formula Compound name Cu + O 2- Cu 2 O Copper oxide Fe 3+ S 2- Cu 2+ Cl - Sn 4+ S 2- V 2+ F - V 3+ Br -
Use numerical prefixes to indicate #atoms of each element in molecule. Second element ends with the -ide suffix a) Examples Boron trifluoride, BF 3 contains one boron atom and three fluorine atoms. Dinitrogen tetroxide, N 2 O 4, is made of two nitrogen atoms and four oxygen atoms.
Molecular Formula Example: Mo 2 O 3 Name Dimolybdenum trioxide CCl 4 PCl 5 SeF 6 As 2 O 5