Sections 1,2 and 3

1
Chapter 6

• Sections 1,2 and 3

2
Key Terms

• Only a few atoms exist as isolated atoms Noble
  Gases
• Molecule
• Smallest electrically neutral unit of a substance
  that still has the properties of the substance.
• Made up of two or more atoms that behave as a
  unit.
• Some are diatomic (appear as pairs)
• Br2I2N2Cl2H2O2F2

3
Molecular Compounds

• Atoms of different elements combine chemically
• Compounds composed of molecules are called
  molecular compounds.
• Some general characteristics
• Low melting and boiling points
• Most are liquids or gases
• Composed of two or more non-metals

4
Ionic Compounds

• Ions atoms or groups of atoms that have
  positive or negative charges (that means the of
  p does not equal the of e-)
• Metallic elements tend to form cations (positive
  charges)
• The protons outnumber the electrons
• The charge is usually written after the symbol
  and to the upper right (Na)
• Cations are named the same as the element.
• Ions behave very differently than the atoms they
  came from.

5

• Anions
• Non-metals usually form anions.
• Negative (electrons outnumber the protons).
• Happens when elements gain electrons
• The name of a typical monatomic anion (1 atom
  that is negative) ends in ide
• Example Cl- chloride

6

• Compounds composed of cations and anions are
  called ionic compounds.
• Usually made of metals with non-metals
• Ionic compounds are electrically neutral
• Usually solids at room temperature and melt at
  extremely high temperatures.

7
Chemical Formulas

• Shows the kinds and number of atoms in the
  smallest representative unit of the substance.
• Use elemental symbols
• Subscripts show haw many of each atom are
  present.
• Example oxygen O2

8
Molecular Formula

• Chemical formula for a molecular compound.
• Tells nothing about structure or arrangement of
  atoms.
• Example carbon dioxide CO2
• One carbon atom and two oxygen atoms tightly
  bound to each other.

9
Formula Unit

• Used for ionic compounds
• Ionic compounds are not molecules
• It is the lowest whole number ration of ions in a
  compound.
• Example NaCl (sodium chloride or table salt) is
  made of one sodium ion and one chloride ion.
  Thus, the ratio is 11 (sodium 1 charge and
  chloride -1 charge)
• Example 2 MgCl2 (magnesium chloride) is made of
  one magnesium cation (2 charge) and two chloride
  anions (-1 each) thus the ratio is 12

10
Laws

• Law of multiple proportions
• If two or more compounds made of the same
  elements exist they are a whole ratio of each
  others composition.
• Law of definite proportions
• Samples of the same compound have the elements
  present in the same ratio.

11
Monatomic Ions

• Ions consisting of only one atom
• Table 6.2 (p143)
• Can be predicted from group on the periodic table.

1A 2A 3A 4A 5A 6A 7A 8A
Li Be2 N-3 O-2 F-
Na Mg2 Al3 P-3 S-2 Cl-
K Ca2 As-3 Se-2 Br-
Rb Sr2 I-
Cs Ba2
12
Transition Metals

• Most can have multiple charges
• Exceptions Silver (Ag), Zinc (Zn2) and
  Cadmium (Cd2)
• Roman Numeral is used to show the charge on the
  cation
• Example Copper (I) Cu1

13
Table 6.3 Page 144
Formula Stock Name Classical Name
Cu Copper (I) Cuprous ion
Cu2 Copper (II) Cupric ion
Fe2 Iron (II) Ferrous ion
Fe3 Iron (III) Ferric ion
Pb2 Lead (II) Plumbous ion
Pb4 Lead (IV) Plumbic ion
Sn2 Tin (II) Stannous ion
Sn4 Tin (IV) Stannic ion
14
Polyatomic Ions

• Tightly bound groups of atoms that behave as a
  unit and carry a charge.
• Change the prefix and suffix to show a change in
  the number of oxygen present.
• Exceptions Cyanide, Hydroxide and ammonium
• Practice with the common ion sheet