1. Names and Formulas of Compounds
Chapter 5
Names and Formulas of Compounds

2. Homework Assigned Problems (odd numbers only)
“Questions and Problems” to 5.61 (begins on page 131)
“Additional Questions and Problems” to 5.95 (page )
“Challenge Questions” to 5.103, (page )

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
Chemical combination
Have a definite composition

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
We will come back to the 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
Note the group each of these representative elements comes from
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
Here are the representative element cations in their groups

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
Ions of opposite charge packed in a highly ordered, three dimensional array

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
It is electrically neutral and has no charge
Packed into a three dimensional lattice

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
In this case, one sodium ion is needed to balance the one chloride. So, it is a 1:1 ratio

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+
• •
Sum of the charges will equal zero
To balance the charge of the nitride, will need to place sodium ions in the formula.
Na• N N • 3-
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)
1A, 2A, 3A groups are the main group elements and a few others Zn, Cd, Ag & Au

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
Allow a space between names of cation and anion
Name of metal______name of nonmetal + -ide

19. Examples KCl NaI Sodium Iodide Potassium Chloride CaF2 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
Sum of the charges must equal zero

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
Most of them are oxyions combine one or more oxygen atoms with another element

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
The names of the most common PA ions ends in –ate. The –ite ending for related ions with one less oxygen atom

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-
Four possibilities by the addition of extra oxygen atoms

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
Correct your notes

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
A space between the names

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
Unlike ionic compounds which involve a reaction between a metal and nonmetal (two dissimilar atoms)
Unlike ionic solids which do not exist as discrete molecules, as an extended array of positive and negative ions

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
The number of vacancies will determine the number of covalent bonds formed
Bonding pair of electrons represented by a dash
Can achieve an octet by accommodating the unpaired electrons of the other atom
This constitutes a single, double, or a triple bond represented by dots or more commonly a dash

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
Bonding pair of electrons represented by a dash
Can achieve an octet by accommodating the unpaired electrons of the other atom

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
Bonding pair of electrons represented by a dash
Can achieve an octet by accommodating the unpaired electrons of the other atom

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
The simplest type of molecular compound, just two nonmetallic elements.
Name the two nonmetals in the order in which they appear in the formula
Remember these compounds are covalently bonded, contain no ions

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
Unlike the ionic compounds the molecular type contain a built-in prefix into each name to indicate the number of atoms each element
Or nitrogen oxide or monoxide
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
The prefix mono- on the first element is not used
Cl2O
dichlorine monooxide
P4O6
tetraphosphorous hexaoxide
dichlorine monoxide
tetraphosphorous hexoxide

51. Examples IF5 B2O3 NO3 iodine pentafluoride diboron trioxide
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
Hydrogen chloride as a gas
Hydrogen iodide as a gas

56. Oxyacids sulfuric acid sulfurous acid
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
It looks like a hydrogen compound of a polyatomic ion