Ionic Compounds

1
Chapter 4

• Ionic Compounds

2
Atoms and Their Ions

• In 1916, Gilbert N. Lewis pointed out that the
  lack of chemical reactivity of the noble gases
  indicates a high degree of stability of their
  electron configurations

3
The Octet Rule

• Octet rule the tendency of group 1A-7A elements
  to react in ways that achieve an outer shell of
  eight valence electrons
• gain electrons a negatively charged ion called
  an anion
• lose electrons a positively charged ion called
  a cation

4
The Octet Rule

• Example in losing one electron, a sodium atom
  forms a sodium ion, which has the same electron
  configuration as neon
• Na (11 electrons) 1s2 2s2 2p6 3s1
• Na (10 electrons) 1s2 2s2 2p6

5
The Octet Rule

• Example in gaining one electron, a chlorine atom
  forms a chloride ion, which has the same electron
  configuration as argon
• chlorine atom (17 electrons) 1s2 2s2 2p6 3s2
  3p5
• chloride ion (18 electrons) 1s2 2s2 2p6 3s2
  3p6

6
The Octet Rule

• The octet rule is good but you have to think
  also
• Real life ideas
• Metals are so Bi doesnt become -3
• Nonmetals so B doesnt become 3

7
Naming Cations

• Elements of Groups 1A, 2A, and Al form only one
  type of cation the name of the cation is the
  name of the metal followed by the word ion
  Always ions

8
Naming Cations

• For cations derived from other metals,
• use Roman numerals to show charge

Example Iron(II) is Fe2 Iron (III) is Fe3
9
Naming Cations
Do Not Use
10
Naming Anions

• For monatomic (containing only one atom) anions,
  add ide to the end
• here are the monatomic anions we deal with most
  often

11
Polyatomic Ions

• common names, where still widely used, are given
  in parentheses

12
Forming Chemical Bonds

• According to the Lewis model
• an atom may lose or gain enough electrons to
  acquire a filled valence shell and become an ion.
  An ionic bond is the result of the force of
  attraction between a cation and an anion.
• an atom may share electrons with one or more
  other atoms to acquire a filled valence shell. A
  covalent bond is the result of the force of
  attraction between two atoms that share one or
  more pairs of electrons.

13
Forming an Ionic Bond

• In forming sodium chloride, NaCl
• we use a single-headed curved arrow to show this
  transfer of one electron

14
Reactions

• Sodium reacts with chlorine
• ION electronic configuration exercise

15
Formulas of Ionic Compounds

• The total number of positive charges must equal
  the total number of negative charges
• lithium ion and bromide ion form LiBr
• barium ion and iodide ion form BaI2
• aluminum ion and sulfide ion form Al2S3
• sodium ion and bicarbonate ion form NaHCO3
• potassium ion and phosphate ion form K3PO4

16
Naming Ionic Compounds

• Binary ionic compounds
• the name of metal from which the positive ion is
  formed followed by the name of the negative ion
  subscripts are ignored
• AlCl3 is aluminum chloride
• LiBr is lithium bromide
• Ag2S is silver sulfide
• MgO is magnesium oxide
• KCl is potassium chloride

17
Naming Ionic Compounds

• Binary ionic compounds of metals that form two
  different cations
• for systematic names, use Roman numerals to show
  charge on the metal ion for common names (not
  used in this class), use the -ous, -ic suffixes
• CuO is copper(II) oxide cupric oxide
• Cu2O is copper(I) oxide cuprous oxide
• FeO is iron(II) oxide ferrous oxide
• Fe2O3 is iron(III) oxide ferric oxide

18
Naming Ionic Compounds

• Ionic compounds that contain polyatomic ions
• name the positive ion first followed by the name
  of the negative ion
• NaNO3 is sodium nitrate
• CaCO3 is calcium carbonate
• NaH2PO4 is sodium dihydrogen phosphate
• NH4OH is ammonium hydroxide
• FeCO3 is iron(II) carbonate ferrous carbonate
• Fe2(CO3)3 is iron(III) carbonate ferric
  carbonate
• CuSO4 is copper(II) sulfate cupric sulfate

19
Forming a Covalent Bond

• A covalent bond is formed by sharing one or more
  pairs of electrons
• the pair of electrons is shared by both atoms
  and, at the same time, fills the valence shell of
  each atom
• example in forming H2, each hydrogen contributes
  one electron to the single bond

20
Molecular Compounds

• Molecular compound a compound in which all bonds
  are covalent
• Naming binary molecular compounds
• the less electronegative element is named first
• prefixes di-, tri-, etc. are used to show the
  number of atoms of each element the prefix
  mono- is omitted when it refers to the first
  atom, and is rarely used with the second atom.
  Exception carbon monoxide
• NO is nitrogen oxide (nitric oxide)
• SF2 is sulfur difluoride
• N2O is dinitrogen oxide (laughing gas)

21
Lewis Structures

• You will build models and draw Lewis Structures
  in Lab.
• You will have to identify the polarity in a
  molecules as well.
• Link to polarity idea