Writing formulas and naming compounds

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Writing formulas and naming compounds

• Unit 7

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Ionic compounds

• One of the most important concepts to understand
  when naming and writing ionic compounds is the
  concept of charge. You must be able to predict
  which ions will have which charge. Therefore,
  lets have a little review!

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Group Metal or non-metal Lose or gain electrons Charge(s)?
Group 1 M Lose 1 1
Group 2 M Lose 2 2
Group 13 M Lose 3 3
Group 14 Non-Metal Metal Gain 4 Lose 2 or 4 -4 2/4
Group 15 Non-Metal Metal Gain 3 Lose 3 or 5 -3 3/5
Group 16 NM Gain 2 -2
Group 17 NM Gain 1 -1
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Transition metals to remember

• Most transition metals can take on different
  charges depending on what they are bonding to.
  However, there are two of these elements that
  will always have a set charge.
• Memorize these!!!
• Ag 1 Zn2

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1
2
3
-4
-3
-2
-1
2 or 4
3 or 5
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Binary Ionic compounds
Binary means 2 types of elements! Not 2 total
atoms.
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Remember from our last unit that we represent
ionic compounds as the lowest whole number ratio
of atoms that make a NEUTRAL formula unit! The
goal of ionic compounds is to make electrons lost
equal electrons gained or, in other words, TO
MAKE CHARGES CANCEL OUT. Therefore, you might
need more than one of an element to make them
cancel! If you need more than one of an element,
you will use a subscript to indicate how many you
need. We do not show a subscript if only one of
that element is needed. Also, in the final
formula, charges are not shown the subscripts
are indicating that charges are canceling out, so
we dont need to show them!
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Elements Ions Make Charges Cancel Final Formula
Calcium Chloride Ca2 and Cl-1 2 -1 -1 0 (need 1 Ca 2 and 2 Cl -1) CaCl2
Aluminum Oxide Al3 and O-2 3 3 -2 -2 -20 (need 2 Al 3 and 3 O -2) Al2O3
Lithium Fluoride Li 1 and F -1 1 -1 0 (need one of each) LiF
Magnesium Phosphide Mg 2 and P -3 2 2 2 -3 -3 0 ( Need 3 Mg 2 and 2 P -3) Mg3P2
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Naming Binary (ionic) Compounds

• Steps Name the metal, then name the non-metal
  with an ide ending.

Formula Compound Name
CaCl2 Calcium chloride
Al2O3 Aluminum oxide
Na2O Sodium oxide
BaI2 Barium iodide
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Binary Ionic compounds WITH those WEIRD
Transition metals!

• We have several metals that can have more than
  one charge for their ions! The metals that like
  to have more than one charge for their ions are
  most of the transition metals, and the metals of
  groups 14 and 15. Therefore, we need to show
  which charge was used for the metal when we write
  the name of the compound. We do this by placing
  the charge of the metal as a roman numeral
  directly after the metals name. We name the
  non-metal with the ide ending.

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COMPOUND IONS MAKE CHARGES CANGEL FINAL FORMULA
Iron (III) oxide Fe3 and O-2 3 3 -2 -2 -2-0 (need 2 Fe3 and 3 O-2) Fe2O3
Tin (IV) chloride Sn4 and Cl-1 4 -1 -1 -1 -1 0 (need 1 Sn4 and 4 Cl-1) SnCl4
Lead (IV) oxide Pb 4 and O -2 4 -2 -2 0 (need 1 Pb 4 and 2 O2-) PbO2
Tin (II) sulfide Sn 2 and S -2 2 -2 0 (need one of each) SnS
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Roman numerals backwards style

• 1) When you see an ionic compound, identify if
  the metal has more than one possible charge or
  not.
• 2) If it does have more than one possible charge,
  use the non-metal to figure out the charge of the
  metal.
• 3) Then, to name the compound,
• name the metal,
• place the charge of the metal using roman
  numerals in brackets, and
• name the non-metal using the ide ending.

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Formula Non-Metal Ion with Charge Find Charge of Metal Name (Use roman numeral for charge)
PbCl2 Cl-1 Pb -1-1 0 (so, Pb has 2 charge) Lead (II) chloride
Cu2S S-2 Cu Cu -2 0 (so, Cu has 1 charge) Copper (I) sulfide
SnO 0 -2 Sn 2 0 (so, Sn has a 2 charge) Tin (II) oxide
CoF3 F -1 Co -1 -1 -1 0 (so , Co has a 3 charge) Cobalt (III) fluoride
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Ternary Ionic Compounds USING POLYATOMIC IONS

• Finally, we need to learn how to name and write
  compounds that have polyatomic ions as part of
  the formula. Luckily for us, this is not much
  different than what weve already learned! By
  the way, these are called TERNARY ionic compounds
  because they have three or more elements. With
  formula writing, the process is the same as it
  was with binary ionic compounds the only
  difference is that if you need more than one of a
  polyatomic ion, we use parentheses before we put
  the final subscript.

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Compound Ions Make Charges Cancel Final Formula
Aluminum nitrate Al3 and NO3-1 3 -1 -1 -1 0 (need 1 Al3 and 3 NO3-1) Al(NO3)3
Ammonium phosphate NH41 and PO4-3 1 1 1 -3 0 (need 3 NH41 and 1 PO4-3) (NH4)3PO4
Calcium hydroxide Ca 2 and OH -1 2 -1 -1 0 (need 1 Ca 2 and 2 OH -1) Ca (OH)2
Copper (II) sulfate Cu 2 and SO4-2 2 -2 0 (need one Cu 2 and one SO4-2) CuSO4
Zinc chlorate
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COVALENT MOLECULES

• A binary covalent compound is composed of two
  different nonmetal elements. For example, a
  molecule of chlorine trifluoride, ClF3 contains 1
  atom of chlorine and 3 atoms of fluorine.

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STEPS TO NAMING

• Step 1 Name the first non-metal using a prefix
  to indicate how many of that element was in the
  compound.
• Step 2 Name the second non-metal using a prefix
  and add the suffix -ide to the end of the name of
  the element.
• EXCEPTION if the compound contains one atom of
  the element that is written first in the name,
  the prefix "mono-" is not used.

atoms1 Prefix atoms Prefix
1 Mono- 6 Hexa-
2 Di- 7 Hepta-
3 Tri- 8 Octa-
4 Tetra- 9 Nona-
5 Penta- 10 Deca-
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Formula Compound Name
CO2 Carbon dioxide
N2O3 Dinitrogen trioxide
SO3 Sulfur trioxide
Name Prefixes Formula
Dinitrogen pentoxide di2, pent5 N2O5
Chlorine monofluoride mono1 ClF
Nitrogen trifluoride Tri3 NF3
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ACIDS

• We tend to place acids into their own category,
  as they follow their own set of rules. Acids are
  always aqueous solutions (aq). An example is HCl
  (aq) named hydrochloric acid. If the substance
  is a gas (such as HCl (g)), then use your ionic
  naming rules i.e. hydrogen chloride.
• Naming Acids
• Name the anion present in the acid.
• Change the suffix of the anion according the
  chart below
• Add the word acid as a last name.
• If the acid has sulfur or phosphorus, we add the
  ur and or back into the name. Ex. H2SO3 ?
  sulfite ? sulfurous acid

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Formula of Acid Anion Name Acid Name
H poly ion (per-ate) Per_____ate Per_____ic acid
H poly ion (-ate) _____ate _____ic acid
H poly ion (-ite) _____ite _____ous acid
H poly ion (hypo-ite) Hypo____ite Hypo___ous acid
H non-metal _____ide Hydro___ic acid
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Balancing Chemical Equations

• Law of Conservation of Mass total mass of
  products must equal total mass of reactants.
• Balance chemical equations by adjusting
  coefficients when necessary. Do not balance
  equations by adjusting subscripts.
• Coefficients are placed in front of compounds,
  never in the middle of a compound.

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Rules to balancing correctly

• Balance metals first.
• Balance polyatomic ions next, if they stay
  together.
• Balance nonmetals (except for Hydrogen and
  Oxygen) next.
• Balance Hydrogen and Oxygen last.

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examples

• Example 1
• 1 Zn 2 HCl ? 1 ZnCl2 1 H2
• Example 2
• 1 Cu 2 AgNO3 ? 1 Cu(NO3)2 2 Ag
• Example 3
• 1 Al2(SO4)3 3 Ca(OH)2 ? 2 Al(OH)3
  3 CaSO4
• Example 4
• 1 Al4C3 12 H2O ? 3 CH4 4 Al(OH)3

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Writing Chemical Equations

• Reactants are written on the left side of a
  chemical equation.
• Products are written on the right side of a
  chemical equation.
• An arrow pointing to the right means yields.

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Directions for writing chemical equations

• 1) Write correct formulas for each of the
  reactants. Put a plus sign between the reactants
  to separate them. (A plus sign means added to
  or reacts with.)
• 2)Draw a yield arrow.
• 3) Write correct formulas for each of the
  products. Put a plus sign between the products
  to separate them. (A plus sign on the product
  side means as well as or in addition to.
• 4) Balance the equation.