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Molecules and Ions. Molecules. Two or more atoms of the same or different elements, covalently bonded together. Molecules are discrete structures, and their formulas represent each atom present in the molecule. Pentane, C 5 H 12. Ions. Cation: A positive ion Mg 2+ , NH 4 + - PowerPoint PPT Presentation
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Molecules and Ions
MoleculesTwo or more atoms of the same or different elements, covalently bonded together.Molecules are discrete structures, and their formulas represent each atom present in the molecule.
Pentane, C5H12
IonsCation: A positive ion
Mg2+, NH4+
Anion: A negative ionCl-, SO4
2-
Ionic Bonding: Force of attraction between oppositely charged ions.
Ionic compounds form crystals, so their formulas are written empirically (lowest whole number ratio of ions).
Predicting Ionic ChargesGroup 1: Lose 1 electron to form 1+ ions H+ Li+ Na+ K+ Rb+ Cs+
Predicting Ionic ChargesGroup 2: Loses 2 electrons to form 2+ ions
Be2+ Mg2+ Ca2+ Sr2+ Ba2+
Predicting Ionic ChargesGroup 13: Loses 3 electrons to form 3+ ions
B3+ Al3+ Ga3+
Predicting Ionic ChargesGroup 14: Loses 4 electrons or gains 4 electrons
Caution! C22- and C4-
are both called carbide
Predicting Ionic ChargesGroup 15: Gains 3 electrons to form 3- ions
N3-
P3-
As3-
NitridePhosphideArsenide
Predicting Ionic ChargesGroup 16: Gains 2 electrons to form 2- ions
O2-
S2-
Se2-
OxideSulfideSelenide
Predicting Ionic ChargesGroup 17: Gains 1 electron to form 1- ions
F1-
Cl1-
Br1-
FluorideChloride
BromideI1- Iodide
Predicting Ionic ChargesGroup 18: Stable Noble gases do not form ions!
Predicting Ionic ChargesGroups 3 - 12: Many transition metals have more than one possible oxidation state.Iron(II) = Fe2+ Iron(III) = Fe3+
Predicting Ionic ChargesGroups 3 - 12: Some transition metals have only one possible oxidation state. Zinc = Zn2+ Silver = Ag+
Writing Ionic Compound Formulas
Example: Barium nitrate1. Write the formulas for the cation and anion, including CHARGES!
Ba2+ NO3-
2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced
( )
2
Writing Ionic Compound Formulas
Example: Ammonium sulfate1. Write the formulas for the cation and anion, including CHARGES!
NH4+ SO4
2-
2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced
( )2
Writing Ionic Compound Formulas
Example: Iron(III) chloride1. Write the formulas for the cation and anion, including CHARGES!
Fe3+ Cl-
2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced
3
Writing Ionic Compound Formulas
Example: Aluminum sulfide1. Write the formulas for the cation and anion, including CHARGES!
Al3+ S2-
2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced
2 3
Writing Ionic Compound Formulas
Example: Magnesium carbonate1. Write the formulas for the cation and anion, including CHARGES!
Mg2+
CO32-
2. Check to see if charges are balanced.
They are balanced
Writing Ionic Compound Formulas
Example: Zinc hydroxide1. Write the formulas for the cation and anion, including CHARGES!
Zn2+ OH-
2. Check to see if charges are balanced. 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
Not balanced
( )2
Writing Ionic Compound Formulas
Example: Aluminum phosphate1. Write the formulas for the cation and anion, including CHARGES!
Al3+ PO43-
2. Check to see if charges are balanced.
They ARE balanced
Naming Ionic CompoundsCation first, then anionMonatomic cation = name of the
elementCa2+ = calcium ion
Monatomic anion = root + -ideCl- = chloride
CaCl2 = calcium chloride
Naming Ionic Compounds
some metal forms more than one cation
use Roman numeral in namePbCl2
Pb2+ is cationPbCl2 = lead(II) chloride
Metals with multiple oxidation states
Binary Molecular/Covalent Compounds
Compounds between two nonmetals First element in the formula is named
first. Keeps its element name Gets a prefix if there is a subscript
on it Second element is named second
Use the root of the element name plus the -ide suffix
Always use a prefix on the second element
List of Prefixes
1 = mon(o) 2 = di 3 = tri 4 = tetra 5 = penta 6 = hexa 7 = hepta 8 = octa 9 = nona 10 = deka
Naming Binary Compounds
P2O5 =
CO2 =
CO =
N2O =
diphosphorus pentoxide
carbon dioxide
carbon monoxide
dinitrogen monoxide
Practice – Write the FormulaCompound Name Compound FormulaCarbon dioxideCarbon monoxideDiphosphorus pentoxideDinitrogen monoxideSilicon dioxideCarbon tetrabromideSulfur dioxidePhosphorus pentabromideIodine trichlorideNitrogen triiodideDinitrogen trioxide
Check next slide for answers
Answers – Write the FormulaCompound Name Compound FormulaCarbon dioxide CO2
Carbon monoxide CODiphosphorus pentoxide P2O5
Dinitrogen monoxide N2OSilicon dioxide SiO2
Carbon tetrabromide CBr4
Sulfur dioxide SO2
Phosphorus pentabromide PBr5
Iodine trichloride ICl3Nitrogen triiodide NI3Dinitrogen trioxide N2O3
Practice – Name the Compounds
Compound Formula
Compound Name
N2O4
SO3
NONO2
As2O5
PCl3CCl4H2OSeF6
Check next slide for answers
Answers – Name the Compounds
Compound Formula
Compound Name
N2O4 dinitrogen tetroxideSO3 sulfur trioxideNO nitrogen monoxideNO2 nitrogen dioxide
As2O5 diarsenic pentoxidePCl3 phosphorus trichlorideCCl4 carbon tetrachlorideH2O dinitrogen monoxideSeF6 selenium hexafluoride