When Atoms Bond

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When Atoms Bond

• Two types of bonds
• Covalentwhen atoms share valence electrons2
  nonmetals
• Ionicwhen atoms lose or gain valence electrons
  metal and nonmetal

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Why do atoms bond?

• All atoms wannabe like the noble gasses with 8
  valence electrons. (or with 2 like Helium)
• Atoms will lose, gain, or share electrons to be
  like a noble gas
• This is called the octet rule!

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IONIC BONDING

• Atoms will lose or gain electrons to achieve an
  octet set of valence electrons.
• Ionsatoms that have lost or gained electrons
• What determines if they will lose or gain??they
  will do whatever is easiest.
• Always made of a metal and a nonmetal!!!

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How do IONS form?

• Remember how group numbers on the periodic table
  tell you the number of valence electrons?
• That helps you determine how many electrons an
  atom will lose or gain.
• Ex Na is in group 1, has 1 valence electron.
  It will lose that electron to become more like

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Valence electrons e- in outermost sub level
Number of valence electrons 1, 2, 3 in groups
3-12
1 2 3 4 5 6 7 8
Group number
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How Na become Na
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Na
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Na
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When Na loses an electron, it has 10 total
electrons and 8 valence electrons just like the
noble gas Ne!!!
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How Mg become Mg2
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Mg2
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Mg
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When Mg loses 2 electrons, it has 10 total
electrons and 8 valence electrons just like the
noble gas Ne!!!
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How Cl become Cl-
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Cl-
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Cl
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When Cl gains 1 electron, it has 18 total
electrons and 8 valence electrons just like Ar
the noble gas !!!
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How Li become Li--an exception to the octet
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Li
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Li
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When Li loses 1 electron, it has 2 total
electrons and 2 valence electrons just like He
the noble gas !!!
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Positive or Negative Ion?

• Atoms are neutral because they have the same
  number of electrons(-) and protons().
• If an atom gains electrons, it becomes a negative
  ion because it now has more electrons(-) that
  protons().
• If an atom loses electrons, it becomes a positive
  ion because it now has more protons() than
  electrons(-).

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Oxidation numbers

• Tell us what charge an ion will have from its
  position on the periodic table!!

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1 2 Oxidation Numbers 3 ?
3- 2- 1-
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How do Ions form Ionic Bonds?

• Negative and positive charges attract.
• Negative and positive ions attract.
• This attraction is what forms an ionic bond to
  make ionic compounds!!!
• Ex Na and Cl- attract to make NaCl
• One ion of each, since they are of equal (1), but
  opposite charges!

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What about Ca2 and Cl-

• It takes 2 Cl- to equal 1 Ca2
• Soooooo the formula is
• CaCl2 and now we have a neutral molecule!!

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What about Na and S2-?

• We must have 2 Na to equal 1 S2-
• So the formula is.
• Na2S

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An Easier Way

• For ionic compounds, always made up of ionsa
  metal and a nonmetal
• Find the charge of each ion
• Cross the charge of each to make the subscript of
  the other ion
• Lose the charges and write the formula!
• Na Cl-

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Crossing the Charges

• Na1 Cl1-
• NaCl final formula

1
1
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Crossing the Charges

• Li1 S2-
• Li2S final formula

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1
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Crossing the Charges

• Ca2 S2-
• Ca2S2 --if both subscripts are
• divisible by the same
  number, then reduce to lowest
  terms
• CaS final formula

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Try These!!

• Ca and Cl
• Mg and F
• Mg and S
• Ca and N
• Mg and O

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Here are the answers!

• Ca and Cl CaCl2
• Mg and F MgF2
• Mg and S MgS
• Ca and N Ca3N2
• Mg and O MgO

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Naming Ionic Compounds

• Name the first element(the metal), name the
  second element, but change the ending to ide
• NaCl sodium chloride
• CaCl2 calcium chloride
• SrO strontium oxide

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Try these!!

• CaCl2
• MgF2
• MgS
• Ca3N2
• MgO

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Answers!

• CaCl2 calcium chloride
• MgF2 magnesium fluoride
• MgS magnesium sulfide
• Ca3N2 calcium nitride
• MgO magnesium oxide

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Now, write the formulas from the names

• Calcium oxide
• Barium nitride
• Sodium sulfide
• Potassium phosphide
• Strontium chloride

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Answers!

• Calcium oxide CaO
• Barium nitride Ba3N2
• Sodium sulfide Na2S
• Potassium phosphide K3P
• Strontium chloride SrCl2

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Write the names from the formulas!

• CaCl2 KCl
• MgF2 SrO
• MgS MgI2
• Ca3N2 BaS
• MgO Li2N

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The answers!

• CaCl2 Calcium chloride KCl Potassium chloride
• MgF2 Magnesium fluoride SrO Strontium oxide
• MgS Magnesium sulfide MgI2 Magnesium iodide
• Ca3N2 Calcium nitride BaS Barium sulfide
• MgO Magnesium oxide Li2N Lithium nitride

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Lewis Dot Diagrams--show number of valence
electrons
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You try some!

• Ca
• H
• Br
• P
• I
• Sr
• F

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Making Compound Lewis Dot Diagrams
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Examples
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MOLECULE LEWIS DIAGRAMS

• 1. Find the total number of electronsTabulate
  the total number of outer energy level electrons
  for all atoms in the molecule. For each atom,
  read the group number.2. Draw a first tentative
  structure The element with the least number of
  atoms is usually the central element. Draw a
  tentative molecular and electron arrangement
  attaching other atoms with single bonds as the
  first guess. Single bonds represented with a line
  represent 2 electrons

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• 3. Add electrons as dots to get octets around
  atomsWhen counting electrons for the octet
  around an atom, count both electrons in a bond
  for each atom and any lone pair electrons.
  Hydrogen, of course, gets only 2 electrons.4.
  Count the total number of electrons in the final
  structure to see if the total agrees with the
  number tabulated in step 1. If not, then move a
  lone pair of electrons into a double bond. Or add
  more lone pairs of electrons.5. Cycle through
  steps 3 and 4 several times until you get it
  right by trial and error.

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Covalent Bonding

• Atoms share electrons to achieve an octet like
  the noble gasses!!
• Made up of 2 nonmetals
• Ex CO2 NO3

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Naming Covalent Compounds

• Name the first element. If it has a subscript of
  more than one, use a prefix to tell how many of
  that atom there are.
• Name the second elementalways use the
  appropriate prefix, even if it is a one! Then
  change the ending to ide!

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Prefixes for Covalent compounds

• 1 - mon(o)
• 2 - di
• 3 - tri
• 4 - tetr(a)
• 5 - pent(a)
• 6 - hex(a)
• 7 - hept(a)
• 8 - oct(a)
• 9 - non(a)
• 10 - dec(a)

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Examples

• CO2 carbon dioxide
• NO3 nitrogen trioxide
• H20 dihydrogen monoxide

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Try these!

• H2S
• CO
• H2O2
• N2O3
• NO4

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Answers!

• H2S Dihydogen monosulfide
• CO Carbon monoxide
• H2O2 Dihydrogen dioxide
• N2O3 Dinitrogen trioxide
• NO4 Nitrogen tetroxide

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How many atoms share?
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• Carbon needs ___ more electrons to have an
  octet.
• Oxygen needs ____ more electrons to have an
  octet.
• So. Carbon will share 2 electrons with O and 2
  oxygens will share 2 each with carbon

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C
O
O
C
O
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Making Compound Lewis Dot Diagrams

• H2

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Polyatomic Ionsatoms that are covalently bonded
that have a charge and act like a single ion

• hydroxide ion, OH-
• Nitrite ion, NO2-
• nitrate ion, NO3-
• acetate ion, C2H3O2-
• carbonate ion, CO32-
• sulfate ion, SO42-
• phosphate ion, PO43-
• ammonium ion, NH4

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Polyatomic ions make ionic compounds with other
ions

• Na and OH-
• make NaOH sodium hydroxide
• K and SO42-
• Make K2SO4 potassium sulfate
• Ca2 and PO43-
• Make Ca3(PO4)2 calcium phosphate

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Formulas and Names of Compounds with Polyatomic
Ions

• Formulastake the charges and cross them to
  become subscripts just as in binary ionic
  compounds
• Namingif the polyatomic ion comes second--name
  the metal and the polyatomic ion just as they
  areNO ide ending!
• --if the polyatomic ion comes first, name
  it, then put an ide ending on the nonmetal ion

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Examples

• Li and SO42-
• Li2SO4
• Lithium sulfate
• Ba2 and OH-
• Ba(OH)2
• Barium hydroxide

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Try these!!

• NH4 and Cl
• Mg and CO32-
• Li and C2H3O2-
• NH4 and N
• Ba and PO43-

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Answers!!

• NH4Cl Ammonium chloride
• MgCO3 Magnesium carbonate
• LiC2H3O2 Lithium acetate
• (NH4)3N Ammonium nitride
• Ba3(PO4)2 Barium phosphate

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Chemical Reactions

• Chemical reactionwhen 2 substance react and
  their atoms are rearranged to form a new
  substance
• Ex
• NaCl LiBr NaBr LiCl

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5 Types of Chemical Reactions

• 1) Combustion when oxygen combines with another
  compound to form water and carbon dioxide.
• --are exothermic-- they produce heat.
• Example-- burning of methane
• CH4 2O2 ---gt CO2 2 H2O

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• 2) Synthesis when two or more simple compounds
  combine to form a more complicated one
• A B ---gt AB
• Na Cl ---gt NaCl

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• 3) Decomposition opposite of a synthesis
  reaction - a complex molecule breaks down to make
  simpler ones.
• AB ---gt A B
• 2 H2O ---gt 2 H2 O2

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• 4) Single replacement when one element trades
  places with another element in a compound.
• A BC ---gt AC B
• 2Mg 2HCl ---gt 2MgCl H2

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• 5) Double replacement when two different
  molecules switch places, forming two entirely
  different compounds.
• AB CD ---gt AD CB
• Ca(NO3)2 2 KI ---gt CaI2 2 KNO3

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Try these!!

• 1)  NaOH KNO3 --gt NaNO3 KOH
• 2)  CH4 2 O2 --gt CO2 2 H2O
• 3)  2 Al 6 NaBr --gt 2 AlBr3 6 Na
• 4)  CaSO4 Mg(OH) 2 --gt Ca(OH) 2 MgSO4

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• 5)  NH4OH HBr --gt H2O NH4Br
• 6)  Sr O2 --gt SrO2
• 7)  Na2CO3 --gt Na2O CO2

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Try these for a quiz!

• Cu AgNO3 ---gt Ag Cu(NO3) 2
• KOH H2SO4 ---gt K2SO4 H2O
• Mg O2 ---gt MgO
• C6H12O6 O2 ---gt CO2 H2O

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Parts of a Chemical Equation
Yields

• 2H2 O2 ---gt 2H2O

Product(s)
Reactant(s)
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Parts of these?

• 1)  NaOH KNO3 --gt NaNO3 KOH
• 2)  CH4 2 O2 --gt CO2 2 H2O
• 3)  2 Al 6 NaBr --gt 2 AlBr3 6 Na

Product(s)
Reactants
Reactant(s)
Product(s)
Reactant(s)
Product(s)
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Balancing Chemical Reactions

• Law of Conservation of Matter
• NaOH KNO3 --gt NaNO3 KOH
• 2 Al 6 NaBr --gt 2 AlBr3 6 Na
• Atoms are not created or destroyedwe must finish
  our chemical reaction with as many atoms of each
  element as when we started

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Lets balance these!

• H2 O2 ---gt H2O
• N2 H2 ---gt NH3
• S8 O2 ---gt SO3
• N2 O2 ---gt N2O

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The Seven Diatomic Substances (plus two friends)

• Hydrogen H2 Nitrogen N2 Oxygen O2 Fluorine F2
  Chlorine Cl2 Bromine Br2 Iodine I2
• I Bring Clay For Our New Houseand Swimming
  Pool
• In addition to the above, phosphorous is P4 and
  sulfur is S8.

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Organic Compounds

• All organic compound
• contain carbon
• come from living things
• Ex CH4 organicprod by organisms
• CO2 inorganicnot from organism
• Contain Hydrogen and Carbonalso called
  hydrocarbons

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Hydrocarbon formulas

• All Carbon and hydrogen atoms
• Carbon likes to make 4 bonds
• Hydrogens around the outside
• All single bonds saturated hydrocarbons
• Not all single bonds unsaturated
• CH4 C4H10 C2H2

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Number of carbons and prefix

• 1 meth- 6 hex-
• 2 eth- 7 hept-
• 3 prop- 8 oct-
• 4 but- 9 non-
• 5 pent- 10 dec-
• Kind of bonds suffix
• All single -ane
• A double -ene
• A triple -yne

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How many hydrogens?

• All single -ane C x 2 2 H
• A double -ene C x 2 H
• A triple -yne C x 1 H