Nomenclature

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Nomenclature

• Honors Chemistry
• Mrs. Partridge

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Chemical Names and Formulas

• Every substance is either an element or a compound

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Chemical Names and Formulas

• In nature, only the noble gas elements tend to
  exist as isolated atoms
• Noble gases are monatomic consisting of single
  atoms

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Chemical Names and Formulas

• A compound consists of more than one kind of atom
• A compound is either molecular or ionic in nature

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Molecules and Molecular Compounds

• A molecule is the smallest electrically neutral
  unit of a substance that still has the properties
  of the substance

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Molecules and Molecular Compounds

• Molecules are made up of 2 or more atoms that act
  as a unit
• Diatomic molecules are composed of 2 atoms (O2)
• Triatomic molecules are composed of 3 atoms (O3
  ozone)

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Molecules and Molecular Compounds

• Atoms of different elements combine chemically to
  form compounds
• Compounds composed of molecules are called
  molecular compounds

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Molecules and Molecular Compounds

• Molecular compounds tend to have relatively low
  melting and boiling points

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Molecules and Molecular Compounds

• Most molecular compounds are composed of 2 or
  more nonmetals
• The molecules of a given molecular compound are
  all the same

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Ions and Ionic Compounds

• Not all compounds are molecular. Many compounds
  are composed of particles called ions
• Ions are atoms or groups of atoms that have a
  positive or negative charge

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Ions and Ionic Compounds

• Ions conduct electricity

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Ions and Ionic Compounds

• Metals tend to form ions by losing one or more
  electrons
• A cation is any atom or group of atoms that has a
  positive charge

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Ions and Ionic Compounds

• For metallic elements, the name of a cation is
  the same as the name of the element

Monatomic cation name of the element Ca2
calcium ion
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Ions and Ionic Compounds

• A metallic atom is chemically different than a
  metallic ion

Na atom is highly reactive
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Ions and Ionic Compounds

• Nonmetals tend to form anions by gaining one or
  more electrons

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Ions and Ionic Compounds

• An anion is an atom or group of atoms that have a
  negative charge

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Ions and Ionic Compounds

• The name of an anion of a nonmetal is NOT the
  same as the element name.
• The name typically ends in ide
• Sulfur Sulfide

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Ions and Ionic Compounds

• Compounds composed of cations and anions are
  called ionic compounds

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Ions and Ionic Compounds

• Although they are composed of ions, ionic
  compounds are electrically neutral
• The TOTAL positive charge the TOTAL negative
  charge

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Ions and Ionic Compounds

• Ionic compounds are usually solid crystals at
  room temperature, and melt at high temperatures

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Chemical Formulas

• A chemical formula shows the kinds and numbers of
  atoms in the smallest representative unit of the
  substance

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Chemical Formulas

• If the molecule has more than one atom of the
  element, a subscript is used
• Cl2
• subscript

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Molecular Formulas

• The chemical formula of a molecular compound is
  called a molecular formula
• CO2

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Molecular Formulas

• Molecular formulas show the composition of a
  molecule, NOT the structure

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Formula Units

• Chemical formulas can also be written for ionic
  compounds
• Formula units are used to represent an ionic
  compound.
• A formula unit is the lowest whole-number ration
  of ions in the compound

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Formula Units

• Ionic charges are used in the criss-cross method
  to derive the correct formula, but they are not
  shown in the formula
• Mg2 Cl-1
• MgCl2

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Monatomic Ions

• For monatomic ions, the ionic charges can be
  determine by using the periodic table

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Predicting Ionic Charges
Group 1
Lose 1 electron to form 1 ions
H
Li
Na
K
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Predicting Ionic Charges
Group 2
Loses 2 electrons to form 2 ions
Be2
Mg2
Ca2
Ba2
Sr2
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Predicting Ionic Charges
Group 13
Loses 3 electrons to form 3 ions
B3
Al3
Ga3
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Monatomic Ions

• Metallic elements tend to LOSE electrons. Metals
  in group IA, 2A, and 3A lose electrons when they
  form cations

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Monatomic Ions

• The ionic charge is positive and is NUMERICALLY
  equal to the group number

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Predicting Ionic Charges
Group 14
Lose 4 electrons or gain 4
electrons?
Neither! Group 13 elements rarely form ions.
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Predicting Ionic Charges
Nitride
N3-
Group 15
Gains 3 electrons to form 3- ions
P3-
Phosphide
As3-
Arsenide
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Predicting Ionic Charges
Oxide
O2-
Group 16
Gains 2 electrons to form 2- ions
S2-
Sulfide
Se2-
Selenide
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Predicting Ionic Charges
F1-
Br1-
Fluoride
Bromide
Group 17
Gains 1 electron to form 1- ions
Cl1-
Chloride
I1-
Iodide
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Monatomic Ions

• The numerical charge of an ion of a Group A
  nonmetal is determined by subtracting the group
  number from 8
• Nonmetals tend to gain electrons and form anions,
  so the sign of the charge is negative

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Predicting Ionic Charges
Group 18
Stable Noble gases do not form ions!
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Monatomic Ions

• Noble gases do not form ions

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Predicting Ionic Charges
Groups 3 - 12
Many transition elements
have more than one possible oxidation state.
Iron(II) Fe2
Iron(III) Fe3
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Predicting Ionic Charges
Groups 3 - 12
Some transition elements
have only one possible oxidation state.
Zinc Zn2
Silver Ag
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Monatomic Ions

• Many transitional metals are capable of forming 2
  cations. There are 2 ways to name them. The
  stock name uses a Roman numeral (I, II, III) in
  parentheses after the symbol indicating the
  charge.

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Monatomic Ions

• The classical naming system uses a root word with
  different suffixes
• The suffix ous is used to name the cation with
  the lower of the 2 ionic charges
• Fe2 is ferrous ion
• The suffix ic is used with the higher of the 2
  ionic charges
• Fe3 is ferric ion

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Polyatomic Ions

• Polyatomic ions are tightly bound groups of atoms
  that behave as a unit and carry a charge

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Polyatomic Ions

• MOST polyatomic ions end in ite or-ate. 3
  exceptions ammonium ion (NH4), cyanide ion
  (CN-) and hydroxide ion (OH-)
• The charge of each polyatomic ion in a given pair
  is the same, but the ite ending indicates one
  less oxygen atom than the ate ending
• NO3- nitrate NO2- nitrite
• SO42- sulfate SO32- sulfite

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Writing Formulas for Binary Ionic Compounds

• Compounds composed of 2 elements are called
  binary compounds
• H2O
• When writing the formula for a binary compound,
  the cation is ALWAYS written first

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Writing Formulas for Binary Ionic Compounds

• The positive charge the negative charge. The
  net ionic charge must 0.
• Written using the criss-cross method, but
  remember to use the LOWEST whole number ratio of
  ions. Ca2 and S2- would criss-cross to Ca2S2,
  but the lowest whole number ratio of ions reduces
  to CaS

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Naming Binary Ionic Compounds

• Name the compound by naming the ions in the order
  written in the formula
• Na and Br- NaBr
• sodium bromide sodium bromide
• ion ion

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Naming Binary Ionic Compounds

• The name of the transition metal that has more
  than one ionic charge must include a Roman
  numeral (or the proper suffix)
• Fe2 and Cl- FeCl2
• iron (II) chloride iron (II) chloride
• ion ion
• Ferrous chloride ferrous chloride
• ion ion

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Ternary Ionic Compounds

• Ternary compounds contain 3 elements
• CaCO3 calcium carbonate
• 1 2 3

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Ternary Ionic Compounds

• Write the formula for each ion in the order
  listed in the name (cation followed by anion),
  then use the criss-cross method to determine the
  subscripts. If more than 1 polyatomic ion is
  needed, place the polyatomic ion formula in
  parentheses, followed by a subscript showing the
  number needed
• Mg2 and OH- Mg(OH)2
• magnesium hydroxide magnesium
• ion ion hydroxide
• When naming ternary ionic compounds from their
  formulas, you must recognize the polyatomic ions
  first

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Binary Molecular Compounds

• Binary molecular compounds are composed of 2
  nonmetals
• They are composed of molecules, NOT IONS, so the
  criss-cross method will NOT work
• Use prefixes to tell how many atoms are present

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Binary Molecular Compounds
Prefix Mono- Di- Tri- Tetra- Penta-
Number 1 2 3 4 5
Prefix Hexa- Hepta- Octa- Nona- Deca-
Number 6 7 8 9 10
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Binary Molecular Compounds

• Always end the name in ide
• The vowel at the end of a prefix is often dropped
  when the name of the element begins with a vowel
  (carbon monoxide not monooxide)
• When a single atom of the FIRST element, omit the
  prefix mono-

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Binary Molecular Compounds

• CO2
• 1st element one carbon, 2nd element, two
  oxygens
• Drop the mono and name di, oxygen changes
  ending
• to oxide
• Carbon dioxide

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Naming Common Acids

• Consider acids to be combinations of anions
  connected to as many hydrogen ions (H) as needed
  to make the molecule electrically neutral
• If the acid is a binary compound
• hydro - root name of anion -ic acid
• H2S hydro sulfur ic acid hydrosulfuric
  acid

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Naming Common Acids

• If the acid contains a polyatomic anion, omit the
  hydro -, and change an ate suffix to ic acid,
  or change an ite suffix to ous acid
• H2SO4 sulfuric acid
• H2SO3 sulfurous acid