Ch' 3 Atoms: The Building Blocks of Matter

1
Ch. 3 Atoms The Building Blocks of Matter

• An atom is the smallest matter that cant be
  divided into smaller matter.
• What is an atom made up of?
• Nucleus
• Proton positive charge
• Neutron neutral charge
• Electron clouds (energy levels)
• Electrons negative charge
• Atom is Greek for indivisible

2

• Daltons Theory Explains the make up of an atom.
• Nucleus ? Protons Neutrons
• Electron Clouds ? Electrons
• Bohrs Model
• Shows the make up of an atom.

3

• Atoms of different elements may combine to form
  chemical compounds.
• In chemical reactions atoms are either combined,
  separated, or rearranged
• Atoms cannot be created nor destroyed.
• Each element can have more than 1 atom.
• Ex. Cl2
• MASS - ATOMIC NEUTRONS

4

• Atoms of the same element may have different
  masses. These are called isotopes.
• Ex. Hydrogen has 3 isotopes ? Protium, deuterium,
  tritium.
• What does the atomic number tell you?
• Number of protons in each atom of an element.
• What does the mass number tell you?
• Total number of protons and neutrons in the
  nucleus of an atom.
• If an element has isotopes for that element they
  are called nuclides.

5

• An atomic mass unit is a standard unit used for
  comparison.
• Carbon has exactly 12 atomic mass units (U) and
  is used as a standard for comparison.
• Each element on the periodic table has an average
  atomic mass.
• Why do you suppose it is an average?
• Average atomic mass is the weighted average of
  the atomic masses of the naturally occurring
  isotopes of an element.
• Ex. Cu ? 69.17 is Cu 63 30.83 is Cu 65.

6

• Mole, Molar Mass, and Avogadros number all help
  describe an element.
• CD ROM
• Mole Roughly the mass of a substance that is
  has 6.02 x 1023 particles (atoms or molecules).
• All of the average atomic masses on the periodic
  table is equal to 1 mole (mol.).
• Ex. B 10.81g 1 mol.
• Ex. Zn 65.39g 1 mol.

7

• Avogadros number is 6.02 X 1023 particles.
• The number of particles (atoms or molecules) in
  exactly one mole is always 6.02 X 1023.
• Ex. B 10.81g 6.02 X 1023.
• Ex. Zn 65.39g 6.02 X 1023.
• Molar mass the mass in grams of one mol. Of a
  pure substance.
• Basically the average atomic mass in grams.
• Ex. B 10.81g 1 mol. 6.02 X 1023.
• Ex. Zn 65.39g 1 mol. 6.02 X 1023.

8

• The molar mass of all elements will always
  contain the same number of atoms, which is 6.02 X
  1023.
• Which atoms are heavier?
• Do the heavier atoms have more atoms in one mole?
• Pg. 90
• Sample Problems from pg. 82-85.