Names and Formulas of Compounds

1
Chapter 5

• Names and Formulas of Compounds

2
Homework

• Assigned Problems (odd numbers only)
• Questions and Problems 5.1 to 5.61 (begins on
  page 131)
• Additional Questions and Problems 5.71 to 5.95
  (page 157-158)
• Challenge Questions 5.97 to 5.103, (page
  158-159)

3
Octet Rule and Ions

• Compounds are pure substances
• The result of a combination of two or more
  elements held together by chemical bonds
• Chemical bonds are the attractive forces that
  hold atoms or ions together
• They can be ultimately broken down into two or
  more simpler substances Elements

4
Octet Rule and Ions

• Two types of attractive forces
• Ionic Involves the transfer of one (or more)
  electrons from one atom (or group) to another
• For example, NaCl
• Covalent When two or more atoms share one or
  more electrons between them
• For example, HF
• In compounds with covalent bonds it is the
  outermost electrons involved in the chemical
  bonding

5
Octet Rule and Ions

• When a compound forms, the atoms must lose, gain,
  or share electrons to produce a noble gas
  electron configuration
• When the sodium atom loses its only valence
  electron, it obtains the electron configuration
  of its nearest noble gas Neon

The octet rule
6
Positive Ions

• Form when an electron or electrons are lost from
  a metal
• Named with element name, then add ion
• Atom becomes charged
• The charge on an ion is equal to the number of
  the electrons lost

Sodium
Sodium Ion
Magnesium
Magnesium Ion
Aluminum
Aluminum Ion
Calcium
Calcium Ion
7
Positive Ions

• Ionic bonding involves transferring one or more
  electrons between two or more atoms
• Produces a () charged atom cation
• Metals in groups IA, IIA, IIIA easily lose
  electrons to acquire the noble gas electron
  configuration

8
Negative Ions

• Form when an electron or electrons are gained
• Named with root of parent atom and adding -ide to
  the end
• Atom becomes charged
• The charge on an ion is equal to the number of
  the electrons gained

Fluorine
Fluoride
Bromine
Bromide
Oxygen
Oxide
Sulfur
Sulfide
9
Negative Ions

• Ionic bonding and the transfer of electrons also
  produces a (-) charged atom anion
• Nonmetals in groups VA, VIA, VIIA will gain the
  necessary number of electrons to acquire the
  noble gas electronic configuration

10
Ionic Compounds

• Compounds which are held together by the
  attraction of positive and negative ions ionic
  compounds
• Solid crystals formed by a very ordered packing
  of oppositely charged ions
• Most ionic compounds are composed of a metal and
  a nonmetal
• High melting temperatures

11
Ionic Compounds

• Solids
• They do not exist as single molecules
• The formula represents the simplest ratio that
  these atoms combine together
• Ions are packed together into a lattice
• Held strongly together, high melting temperature

12
Charge Balance in Ionic Compounds

• Binary ionic compounds are composed of only two
  elements (metal and nonmetal)
• The symbol of the cation always precedes the
  symbol of the anion
• The sum of the positive charges (cation) must
  equal the sum of the negative charges (anion)
• Net charge is zero
• Subscripts written as whole numbers indicate the
  number of each ion in the formula unit

13
Subscripts in Formulas

• Sodium Chloride
• Formed from sodium and chlorine atoms
• An ionic bond forms consisting of a sodium ion
  ( charge) and a chloride ion (-
  charge)

• Each sodium loses one electron to achieve an
  octet
• Each chlorine atom gains one electron to achieve
  an octet
• Formula is NaCl

14
Subscripts in Formulas

• Magnesium Chloride
• Formed from magnesium and two chlorines
• An ionic bond forms consisting of a magnesium ion
  (2 charge) and
• two chloride ions (- charge each)

• Each magnesium loses two electrons to achieve an
  octet
• Each chlorine atom gains one electron to achieve
  an octet
• Formula is MgCl2

15
Writing Ionic Formulas from Ionic Charges

• Subscripts in a formula represent the number of
  positive and negative ions
• Write the formula for the ionic compound
  containing Na and N3-

Na

Na

Na
N
3-


N
Na









Na
Na


Gains 3e-

Net charge 3(1) 1(3-)0 Formula Na3N
Each loses 1e-
16
Naming and Writing Ionic Formulas

• Ionic Compounds Containing Two Elements
• Compounds containing a metal and a nonmetal are
  binary ionic compounds
• Single Cation Metals Form one positive ion
• Multiple Cation Metals Form more than one
  positive ion
• The systematic naming uses the name of the cation
  first, followed by the name of the anion
• Subscripts in the formula are not included in the
  name

17
Types of Metal Ions

• Single Cation Metals
• Form only one type of ion (one possible charge)
• Main group metals in groups IA, IIA, and some
  IIIA
• i.e. Sodium only forms one ion (Na) in chemical
  reactions
• Determine charge by position on the periodic
  table (also see table 5.3 on page 136)

18
Naming Ionic Compounds Containing Two Elements

• Name metal cation first, name nonmetal anion
  second
• Single metal cation name is the metal name only,
  drop the word ion
• Nonmetal anion named by changing the ending on
  the nonmetal name to -ide

Name of metal______name of nonmetal -ide
19
Examples

• KCl
• Potassium Chloride
• Na3P
• Sodium Phosphide
• Rb2S
• Rubidium Sulfide
• Mg3N2
• Magnesium Nitride

• NaI
• Sodium Iodide
• CaF2
• Calcium Fluoride
• Li2O
• Lithium Oxide
• AgCl
• Silver Chloride

20
Types of Metal Ions

• Multiple Cation Metals
• Form two or more types of ions (variable possible
  charge)
• Transition metals in groups 3B to 12B, and some
  4A and 5A
• For example, Iron forms two ions (Fe2 and Fe3)
  in chemical reactions
• Determine charge by the stock system for naming
  ions
• The metal name followed by a Roman numeral in
  parentheses to indicate its charge (see table 5.4
  on page 137)

21
Multiple Cation Metal Compounds

• Metal listed first in formula name (same order
  as for Type I compounds)
• Determine metal cation charge from anion charge
• Use the metal name (cation) first followed by a
  Roman numeral in parentheses to indicate its
  charge
• Common multiple cations in Table 5.4, page 137
• Nonmetal anion named by changing the ending on
  the nonmetal name to -ide

22
Determining the Charge of the Cation from the
Anion

• Determine the charge of Cu in Cu2O
• Write the name of the compound
• Determine the charge of the cation from the anion
• Cu2O - the nonmetal anion is O, since it is in
  Group 6A, its charge is -2
• Since there are 2 Cu ions in the formula and the
  total positive charge is 2, divide by the number
  of cations so each Cu has a 1 charge

23
Naming Ionic Compound with Variable Charge Metal
Ions

• Name the cation by its element name and use a
  Roman numeral in parenthesis to indicate its
  charge
• Copper (I)
• Name the anion by changing the last part of its
  element name to ide
• Oxygen
• Write the name of the cation first and the name
  of the anion second

oxide
copper (I) oxide
24
Examples

• FeI3
• 1(?)3(-1)0
• Iron (III) Iodide
• Cu2O
• 2(?)1(-2)0
• Copper (I) Oxide
• SnBr2
• 1(?)2(-1)0
• Tin (II) Bromide

25
Examples

• SnI4
• 1(?)4(-1)0
• Tin (IV) iodide
• HgO
• 1(?)1(-2)0
• Mercury (II) Oxide
• MnCl2
• 1(?)2(-1)0
• Manganese (II) Chloride

26
Writing Formulas from the Name of an Ionic
Compound

• Usually involves a metal and a nonmetal
• Identify the cation and the anion
• Balance the charges to write the formula
• If it is a multiple cation metal, the Roman
  numeral determines the charge of the cation
• When writing the formula, take the name of the
  cation first, followed by the name of the anion

27
Writing Formulas from the Name of an Ionic
Compound

• Compound name is lithium chloride
• Li and Cl- are the ions
• Balance the charges
• Write the formula
• LiCl is the formula using the subscripts from the
  charge balance

1
1
28
Writing Formulas from the Name of an Ionic
Compound

• Compound name is iron (III) oxide
• Fe3 and O2- are the ions
• Balance the charges
• Write the formula
• Fe2O3 is the formula using the subscripts from
  the charge balance

2
3
29
Polyatomic Ions

• A group of atoms covalently bonded together into
  a single unit
• The unit obtains a charge
• Most PA ions are negatively charged
• Oxyions (anions) P, S, C, or N covalently bound
  to one or more oxygens
• Never occur independently, always associated with
  ions of opposite charge
• Only one PA is positively charged
• ammonium ion

30
Naming Polyatomic Ions

• Must memorize name, formula and charge (Table 5.6
  on page 142). Look for relationships between ions
• Oxyions The number of oxygen atoms bonded to the
  same element (i.e. P, S, or N) will determine
  the name of the ion
• ate is most common
• ite has one less oxygen bonded

31
Polyatomic Ions

• ate, ite pairs of ions
• The ion in the pair with the most oxygens is
  always the ate ion
• The ion in the pair with one less oxygen is
  always the ite ion
• Ion pair with a -3 charge
• phosphate PO43-, phosphite PO33-
• Ion pair with a -2 charge
• sulfate (SO42-), sulfite (SO32-)
• Ion pair with a -1 charge
• nitrate (NO3-), nitrite (NO2-)

32
Polyatomic Ions

• Group 7A elements can form more than two types of
  polyatomic ions (oxyions)
• Additional prefixes are used to differentiate the
  ions
• See page 142 (class text) and page 330 (lab text)
• The number of oxygens attached to the central
  atom has an effect on the name of the ion
• e.g. Polyatomic ions of chlorine, bromine and
  iodine

33
Polyatomic Ions

• Example Polyatomic ions of chlorine
• -ate ion
• chlorate ClO3-
• -chlorate ion with 1 more O than chlorate, use
  per- prefix
• perchlorate ClO4-
• - chlorate ion with 1 less O, use -ite suffix
• chlorite ClO2-
• -chlorite ion with 1 less O, use hypo- prefix
• hypochlorite ClO-

34
Writing Formulas for Compounds Containing
Polyatomic Ions

• Formulas are written like binary ionic compounds
• Consider polyatomic ions as single units with a
  certain charge
• Obtain the correct ratio of cation to anion to
  achieve a net charge of zero
• Use parentheses if more than one of the same PA
  unit is needed in a formula
• Use subscripts to indicate the number of a
  particular ion in a formula

35
Writing Formulas for Compounds Containing
Polyatomic Ions

• Compound name is magnesium carbonate
• Mg2 and CO32- are the ions
• Balance the charges
• Write the formula
• MgCO3 is the formula using the subscripts from
  the charge balance

1
1
36
Writing Formulas for Compounds Containing
Polyatomic Acids

• Compound name is calcium nitrate
• Ca2 and NO3- are the ions
• Balance the charges
• Write the formula
• Ca(NO3)2 is the formula using the subscripts from
  the charge balance

1
2
37
Naming Compounds Containing Polyatomic Ions

• Named the same way as binary ionic compounds
• Positive ion (metal) name is written first
• Polyatomic ions name follows the metal
• No prefixes are used in the name
• Cation Check to see if metal is single or
  multiple cation
• Use the name of the PA ion given in table 5.6 on
  page 142

38
Writing Formulas for Compounds Containing
Polyatomic Ions

• Compound name is iron (III) sulfate
• Fe3 and SO42- are the ions
• Balance the charges
• Write the formula
• Fe2(SO4)3 is the formula using the subscripts
  from the charge balance

2
3
39
Writing Formulas for Compounds Containing
Polyatomic Ions

• Compound name is ammonium phosphate
• NH4 and PO43- are the ions
• Balance the charges
• Write the formula
• (NH4)3PO4 is the formula using the subscripts
  from the charge balance

3
1
40
Naming Compounds Containing Polyatomic Ions

• CaSO4
• calcium sulfate
• Ca2 and SO42-
• Li2CO3
• lithium carbonate
• Li, CO32-
• Al(NO3)3
• aluminum nitrate
• Al3, NO3-

41
Summary of Naming Ionic Compounds

• Summary of guidelines when writing binary ionic
  compound
• The symbol of the cation always precedes the
  anion
• The sum of the positive charges must equal the
  sum of the negative charges
• A net charge of zero
• Whole numbers are written as subscripts to
  indicate the number of each ion in the formula

42
Covalent Compounds and Their Names

• Involves a bond between two nonmetals
• Bonds occur between similar or identical atoms
• Nonmetals such as O, Br, or N do not tend to lose
  electrons (tend to gain them)
• Electrons are shared and not transferred between
  atoms forming covalent bonds
• Exist as individual molecule

43
Formation of a Hydrogen Molecule

• The simplest covalent bonding condition
• Hydrogen has one 1s electron
• H atom requires one additional electron to obtain
  the stable noble gas configuration of helium
• Each H atom contributes its one electron
• The electron pair shared by the two atoms,
  forming diatomic hydrogen H2

44
Formation of Octets in Covalent Molecules

• Two identical nonmetal atoms
• Each atom will share valence electrons with the
  other
• The shared pair of electrons allow each atom to
  achieve a stable noble gas configuration
• This configuration can be achieved by a single,
  double, or triple shared pair of electrons

45
Formation of Octets in Covalent Molecules

• Two identical nonmetal atoms
• H atom exists as a diatomic molecule by achieving
  a duet of electrons
• F, Cl, Br, I, O, N exist as diatomic molecules by
  achieving an octet of electrons in their valence
  shells

46
Sharing Electrons Between Atoms of Different
Elements

• Each atom will share valence electrons with the
  other forming a shared pair of bonding electrons
  (achieves a stable noble gas configuration)

• Two nonidentical nonmetal atoms
• The number of covalent bonds an atom forms will
  equal the number of electrons needed to form a
  noble gas configuration
• Each vacancy unpaired electron combination in
  the valence shell can be used to form a
  two-electron bond

47
Names and Formulas of Covalent Compounds

• Molecular binary compounds
• Composed of two nonmetal elements
• Naming a compound
• Use the full (element ) name for the first
  nonmetal
• Add the ide ending to the full name of the
  second nonmetal
• Second nonmetal named like the nonmetal in binary
  ionic compounds (anion)
• Indicate the number of atoms by adding numerical
  prefixes

48
Names and Formulas of Covalent Compounds (table
5.11, page 151)
Subscript Prefix used
1 mono (Usually omitted on the first atom)
2 di
3 tri
4 tetra
5 penta
6 hexa
7 hepta
8 octa
9 nona
10 deca
49
Names and Formulas of Covalent Compounds

• In ionic compounds the subscripts are not
  mentioned in the name
• Many compounds can exist for many pairs of
  nonmetallic elements (i.e. nitrogen and oxygen)

BaCl2 barium chloride barium dichloride
Na2SO4 sodium sulfate disodium sulfate
nitrogen monoxide
nitrogen dioxide
dinitrogen monoxide
50
Molecular Binary (Covalent) Compounds

• Naming binary molecular compounds from a formula
• Name the first nonmetal by its element name
• Name the second nonmetal by adding the ide
  suffix
• Add the prefixes to indicate the number of atoms
• Whenever the vowels a and o or o and o appear
  together, the first vowel is dropped from the
  prefix for easier pronunciation

Cl2O dichlorine monooxide
P4O6 tetraphosphorous hexaoxide
dichlorine monoxide
tetraphosphorous hexoxide
51
Examples

• IF5
• iodine pentafluoride
• B2O3
• diboron trioxide
• NO3
• nitrogen trioxide

52
Examples

• AsCl3
• arsenic trichloride
• CO2
• carbon dioxide
• CO
• carbon monoxide

53
Molecular Binary (Covalent) Compounds

• When writing a formula from the name of a binary
  molecular compound
• You must know definition of the numerical
  prefixes used in naming covalent compounds (see
  table 5.11)
• (you MUST memorize these prefixes)
• Write the symbols in order the elements appear in
  the name
• Identify the prefixes with the appropriate
  subscripts

54
Acids (Section 14.1)

• Produce H when dissolved in water
• Composed of H (cation) and an anion
• Binary acids have H cation and a nonmetal anion
• Oxyacids have H cation and a polyatomic anion
  (contain oxygen)

55
Naming Binary Acids

• Use the prefix hydro- before the root name of the
  element
• Add the suffix -ic and the word acid to the root
  name for the element
• Example HCl
• hydrochloric acid
• Example HI
• hydroiodic acid

56
Oxyacids

• Produce H and a polyatomic ion when dissolved in
  water
• Composed of hydrogen, oxygen, and another
  nonmetal
• Use the root name of the polyatomic ion
• If it ends in -ate use the suffix -ic acid
• If it ends in -ite use the suffix -ous acid
• Example H2SO4 (from SO42- ,sulfate ion)
• sulfuric acid
• Example H2SO3 (from SO32- ,sulfite ion)
• sulfurous acid