formulas and names september14, 2011. compounds chemical compounds are two or more elements...
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Formulas and NamesSeptember14, 2011
CompoundsChemical compounds are two or more
elements chemically combined in fixed proportions
WHY do elements combine?The OCTET rule: atoms are most stable when their
outer-most energy levels are full of electronsAtoms want to be like the noble gases!
The first energy level can hold only TWO electronsThe second and beyond generally hold EIGHT electrons
How do elements combine?Molecular compounds
Share electrons
How do elements combine?Ionic Compounds
Some elements steal electrons from other elements!The result is IONS with opposite electric chargesOpposite charges attractCation = +Anion = -
How do elements combine?How many electrons is each element likely to gain or lose?
Molecular and Ionic Compounds
CharacteristicMolecular
CompoundsIonic Compounds
Unit Molecule Formula Unit
Type of elements NonmetalsMetals combined with
nonmetals
Phase of Matter Solid, liquid or gas Solids
Melting PointLow (usually below
300oC)High (usually above
300oC)
Representing CompoundsChemical Formulas = shows the kinds and
numbers of atoms in the smallest representative unit of the compoundEx) diatomic formulas
H2 F2 O2 Cl2
Representing compounds
NH3
Representing CompoundsFormula units – ionic compounds
Represent smallest whole number ratio of ions
16 Na+ and 16 Cl- Na16Cl16
Na1Cl1
NaCl
Naming CompoundsBinary Ionic Compounds (TWO ions)
‘cation name’ anion name –ide’
1A 2A 3A 4A 5A 6A 7A
Li+ Be2+ Al3+ N3- O2- F-
Na+ Mg2+ P3- S2- Cl-
K+ Ca2+ As3- Se2- Br-
Rb+ Sr2+ I-
Cs+ Ba2+
Ionic Charges of Common Elements
Naming CompoundsNaClBeOK2OAlF3
Calcium sulfideAluminum phosphideRubidium bromideMagnesium oxide
Naming CompoundsPolyatomic Ions
Sometimes atoms that are sharing electrons with each other will steal electrons from other atoms!!
Common Polyatomic IonsKnow these!!
Formula Name Charge
CO3 Carbonate -2
NO3 Nitrate -1
NH4 Ammonium +1
PO4 Phosphate -3
SO4 Sulfate -2
Writing FormulasIonic formula units must have a net ZERO chargePositive ion charges must balance negative ion
charges
Writing FormulasMagnesium fluoride
MgF2
Writing formulasPb2+ and Cl-
Al3+ and F-
K+ and Se2-
Sr2+ and P3-
Al3+ and S2-
K + and OH-
Cu2+ and NO3-
Al 3+ and CO32-
Today’s LabGOGGLES GOGGLES GOGGLESPipetteWell plate
Today’s LabEach reaction…CATION + ANION Ionic Compound
reactants yields products
Most ions are soluble, which means they will dissolve in water. However, today’s reactions result in insoluble products… we call these precipitates.