Elements and Compounds

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Elements and Compounds

• elements combine together to make an almost
  limitless number of compounds
• the properties of the compound are totally
  different from the constituent elements

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Formation of Water from Its Elements
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Bond Types

• two general types of bonding between atoms found
  in compounds, ionic and covalent
• ionic bonds result when electrons have been
  transferred between atoms, resulting in
  oppositely charged ions that attract each other
• generally found when metal atoms bonded to
  nonmetal atoms
• covalent bonds result when two atoms share some
  of their electrons
• generally found when nonmetal atoms bonded
  together

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Molecular View of Elements and Compounds
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Molecular Elements

• Certain elements occur as 2 atom molecules
• Rule of 7s
• Other elements occur as polyatomic molecules
• P4, S8, Se8

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Writing Formulas for Ionic Compounds

• Write the symbol for the metal cation and its
  charge
• Write the symbol for the nonmetal anion and its
  charge
• Charge (without sign) becomes subscript for other
  ion
• Reduce subscripts to smallest whole number ratio
• Check that the sum of the charges of the cation
  cancels the sum of the anions

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Metal Cations

• Metals with Variable
• Charges
• metals whose ions can have more
  than one
• possible charge
• determine charge by
• charge on anion
• cation name metal name with Roman numeral
  charge in parentheses

• Metals with Invariant Charge
• metals whose ions can only have one possible
  charge
• Groups 1A1 2A2, Al3, Ag1, Zn2, Sc3
• cation name metal name

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Naming Monatomic Nonmetal Anion

• determine the charge from position on the
  Periodic Table
• to name anion, change ending on the element name
  to ide

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Write the formula of a compound made from
aluminum ions and oxide ions

• Write the symbol for the metal cation and its
  charge
• Write the symbol for the nonmetal anion and its
  charge
• Charge (without sign) becomes subscript for other
  ion
• Reduce subscripts to smallest whole number ratio
• Check that the total charge of the cations
  cancels the total charge of the anions

Al3 column 3A
O2- column 6A
Al3 O2-
Al2 O3
Al (2)(3) 6 O (3)(-2) -6
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Practice - What are the formulas for compounds
made from the following ions?

• potassium ion with a nitride ion
• calcium ion with a bromide ion
• aluminum ion with a sulfide ion

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Practice - What are the formulas for compounds
made from the following ions?

• K with N3- K3N
• Ca2 with Br- CaBr2
• Al3 with S2- Al2S3

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Practice - What are the formulas for compounds
made from the following ions?

• copper(II) ion with a nitride ion
• iron(III) ion with a bromide ion

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Practice - What are the formulas for compounds
made from the following ions?

• Cu2 with N3- Cu3N2
• Fe3 with Br- FeBr3

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Formula-to-NameRules for Ionic Compounds

• made of cation and anion
• some have one or more nicknames that are only
  learned by experience
• NaCl table salt, NaHCO3 baking soda
• write systematic name by simply naming the ions
• If cation is
• metal with invariant charge metal name
• metal with variable charge metal name(charge)
• polyatomic ion name of polyatomic ion
• If anion is
• nonmetal stem of nonmetal name ide
• polyatomic ion name of polyatomic ion

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Example Naming Binary Ionic with Invariant
Charge Metal CsF

• Identify cation and anion
• Cs Cs because it is Group 1A
• F F- because it is Group 7A
• Name the cation
• Cs cesium
• Name the anion
• F- fluoride
• Write the cation name first, then the anion name
• cesium fluoride

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Name the following compounds

• KCl
• MgBr2
• Al2S3

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Name the following compounds

• KCl potassium chloride
• MgBr2 magnesium bromide
• Al2S3 aluminum sulfide

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Determining the Charge on a Cation with Variable
Charge Au2S3

• determine the charge on the anion
• Au2S3 - the anion is S, since it is in Group 6A,
  its charge is -2
• determine the total negative charge
• since there are 3 S in the formula, the total
  negative charge is -6
• determine the total positive charge
• since the total negative charge is -6, the total
  positive charge is 6
• divide by the number of cations
• since there are 2 Au in the formula and the
  total positive charge is 6, each Au has a 3
  charge

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Example Naming Binary Ionic with Variable
Charge Metal CuF2

• Identify cation and anion
• F F- because it is Group 7
• Cu Cu2 to balance the two (-) charges from 2
  F-
• Name the cation
• Cu2 copper(II)
• Name the anion
• F- fluoride
• Write the cation name first, then the anion name
• copper(II) fluoride

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Name the following compounds

• TiCl4
• PbBr2
• Fe2S3

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Name the following compounds

• TiCl4 titanium(IV) chloride
• PbBr2 lead(II) bromide
• Fe2S3 iron(III) sulfide

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Compounds Containing Polyatomic Ions

• Polyatomic ions are single ions that contain
  more than one atom
• Often identified by (ion) in formula
• Name and charge of polyatomic ion do not change
• Name any ionic compound by naming cation first
  and then anion

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Some Common Polyatomic Ions
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Example Naming Ionic Compounds Containing a
Polyatomic Ion Na2SO4

• Identify the ions
• Na Na because in Group 1A
• SO4 SO42- a polyatomic ion
• Name the cation
• Na sodium, metal with invariant charge
• Name the anion
• SO42- sulfate
• Write the name of the cation followed by the name
  of the anion
• sodium sulfate

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Example Naming Ionic Compounds Containing a
Polyatomic Ion Fe(NO3)3

• Identify the ions
• NO3 NO3- a polyatomic ion
• Fe Fe3 to balance the charge of the 3 NO3-1
• Name the cation
• Fe3 iron(III), metal with variable charge
• Name the anion
• NO3- nitrate
• Write the name of the cation followed by the name
  of the anion
• iron(III) nitrate

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Name the following

• NH4Cl
• Ca(C2H3O2)2
• Cu(NO3)2

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Name the following

• NH4Cl ammonium chloride
• Ca(C2H3O2)2 calcium acetate
• Cu(NO3)2 copper(II) nitrate

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Practice - What are the formulas for compounds
made from the following ions?

• aluminum ion with a sulfate ion
• chromium(II) with hydrogen carbonate

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Practice - What are the formulas for compounds
made from the following ions?

• Al3 with SO42- Al2(SO4)3
• Cr2 with HCO3- Cr(HCO3)2

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Hydrates

• hydrates are ionic compounds containing a
  specific number of waters for each formula unit
• water of hydration often driven off by heating
• in formula, attached waters follow
• CoCl26H2O
• in name attached waters indicated by suffix
  -hydrate after name of ionic compound
• CoCl26H2O cobalt(II) chloride hexahydrate
• CaSO4½H2O calcium sulfate hemihydrate

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Practice

• What is the formula of magnesium sulfate
  heptahydrate?
• What is the name of NiCl26H2O?

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Practice

• What is the formula of magnesium sulfate
  heptahydrate? MgSO4?7H2O
• What is the name of NiCl26H2O?
• nickel(II) chloride hexahydrate

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Writing Names of Binary Molecular Compounds of 2
Nonmetals

• Write name of first element in formula
• element furthest left and down on the Periodic
  Table
• use the full name of the element
• Writes name the second element in the formula
  with an -ide suffix
• as if it were an anion, however, remember these
  compounds do not contain ions!
• Use a prefix in front of each name to indicate
  the number of atoms
• Never use the prefix mono- on the first element

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Subscript - Prefixes

• 1 mono-
• not used on first nonmetal
• 2 di-
• 3 tri-
• 4 tetra-
• 5 penta-

• 6 hexa-
• 7 hepta-
• 8 octa-
• 9 nona-
• 10 deca-

• drop last a if name begins with vowel

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Example Naming Binary Molecular BF3

• Name the first element
• boron
• Name the second element with an ide
• fluorine ? fluoride
• Add a prefix to each name to indicate the
  subscript
• monoboron, trifluoride
• Write the first element with prefix, then the
  second element with prefix
• Drop prefix mono from first element
• boron trifluoride

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Name the following

• NO2
• PCl5
• I2F7

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Name the following

• NO2 nitrogen dioxide
• PCl5 phosphorus pentachloride
• I2F7 diiodine heptafluoride

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Example Binary Moleculardinitrogen pentoxide

• Identify the symbols of the elements
• nitrogen N
• oxide oxygen O
• Write the formula using prefix number for
  subscript
• di 2, penta 5
• N2O5

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Write formulas for the following

• dinitrogen tetroxide
• sulfur hexafluoride
• diarsenic trisulfide

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Write formulas for the following

• dinitrogen tetroxide N2O4
• sulfur hexafluoride SF6
• diarsenic trisulfide As2S3

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Acids

• acids are molecular compounds that form H when
  dissolved in water
• to indicate the compound is dissolved in water
  (aq) is written after the formula
• not named as acid if not dissolved in water
• sour taste
• dissolve many metals
• like Zn, Fe, Mg but not Au, Ag, Pt
• formula generally starts with H
• e.g., HCl, H2SO4

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Reaction of Acids with Metals
H2 gas
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Acids

• Contain H1 cation and anion
• in aqueous solution
• Binary acids have H1 cation and nonmetal anion
• Oxyacids have H1 cation and polyatomic anion

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Naming Binary Acids

• write a hydro prefix
• follow with the nonmetal name
• change ending on nonmetal name to ic
• write the word acid at the end of the name

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Example - Naming Binary Acids HCl(aq)

• Identify the anion
• Cl Cl-, chloride because Group 7A
• Name the anion with an ic suffix
• Cl- chloride ? chloric
• Add a hydro- prefix to the anion name
• hydrochloric
• Add the word acid to the end
• hydrochloric acid

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Naming Oxyacids

• if polyatomic ion name ends in ate, then change
  ending to ic suffix
• if polyatomic ion name ends in ite, then change
  ending to ous suffix
• write word acid at end of all names

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Example Naming Oxyacids H2SO4(aq)

• Identify the anion
• SO4 SO42- sulfate
• If the anion has ate suffix, change it to ic.
  If the anion has ite suffix, change it to -ous
• SO42- sulfate ? sulfuric
• Write the name of the anion followed by the word
  acid
• sulfuric acid
• (kind of an exception, to make it sound nicer!)

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Example Naming Oxyacids H2SO3(aq)

• Identify the anion
• SO3 SO32- sulfite
• If the anion has ate suffix, change it to ic.
  If the anion has ite suffix, change it to -ous
• SO32- sulfite ? sulfurous
• Write the name of the anion followed by the word
  acid
• sulfurous acid

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Name the following

• H2S
• HClO3
• HNO2

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Name the following

• H2S hydrosulfuric acid
• HClO3 chloric acid
• HNO2 nitrous acid

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Writing Formulas for Acids

• when name ends in acid, formulas starts with H
• write formulas as if ionic, even though it is
  molecular
• hydro prefix means it is binary acid, no prefix
  means it is an oxyacid
• for oxyacid, if ending is ic, polyatomic ion
  ends in ate if ending is ous, polyatomic ion
  ends in ous

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Example Binary Acidshydrosulfuric acid
in all acids the cation is H

• Write the symbol for the cation and its charge
• Write the symbol for the anion and its charge
• Charge (without sign) becomes subscript for other
  ion
• Add (aq) to indicate dissolved in water
• Check that the total charge of the cations
  cancels the total charge of the anions

H
hydro means binary
S2-
H S2-
H2S
H2S(aq)
H (2)(1) 2 S (1)(-2) -2
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Example Oxyacidscarbonic acid
in all acids the cation is H

• Write the symbol for the cation and its charge
• Write the symbol for the anion and its charge
• Charge (without sign) becomes subscript for other
  ion
• Add (aq) to indicate dissolved in water
• Check that the total charge of the cations
  cancels the total charge of the anions

H
no hydro means polyatomic ion
CO32-
-ic means -ate ion
H CO32-
H2CO3
H2CO3(aq)
H (2)(1) 2 CO3 (1)(-2) -2
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Example Oxyacidssulfurous acid
in all acids the cation is H

• Write the symbol for the cation and its charge
• Write the symbol for the anion and its charge
• Charge (without sign) becomes subscript for other
  ion
• Add (aq) to indicate dissolved in water
• Check that the total charge of the cations
  cancels the total charge of the anions

H
no hydro means polyatomic ion
SO32-
-ous means -ite ion
H SO32-
H2SO3
H2SO3(aq)
H (2)(1) 2 SO3 (1)(-2) -2
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Practice - What are the formulas for the
following acids?

• chlorous acid
• phosphoric acid
• hydrobromic acid

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Practice - What are the formulas for the
following acids?

• H with ClO2 HClO2
• H with PO43 H3PO4
• H with Br HBr

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• The halogen can occur with up to four different
  oxoacids
• The oxoacid with the most oxygens has the prefix
  per- the one with the least has the prefix hypo-

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• Anions are produced when oxoacids are neutralized
• There is a simple relationship between the name
  of the polyatomic ion and the parent acid
• ic acids give ate ions
• -ous acids give ite ions
• In naming polyatomic anions, the prefixes per-
  and hypo- carry over from the parent acid