Chapter 5

Dalton's Atomic Theory

  1. All elements are composed of tiny indivisible particles called atoms (small particles that can no longer be divided and still maintain the properties of that element).
  2. Atoms of the same element are identical. The atoms of any one element are different from those of any other element.
  3. Atoms of different elements can physically mix together or can chemically combine with one another in simple whole number ratios to form compounds.
  4. chemical reactions occur when atoms are separated, joined, or rearranged. Atoms of one element are never changed into atoms of another element as a result of a chemical reaction.

Atoms are made up of subatomic particles:
  • Electrons - e-
  • Protons - p+
  • Neutrons - N

Atomic Number
  • Identifies the number of protons in the nucleus of an atom.
  • Each element has a specific number of protons
  • The atom of an element is always neutral, therefore, the number of protons and the number of electrons is the same.

How to find the number of neutrons in the nucleus of an atom:

Atomic mass - Atomic Number = Number of Neutrons

Atomic Mass Unit (amu)

  • total mass of each element and the atoms of each of those elements
2 atoms of hydrogen and 1 atom of oxygen H - 2 x 1.01 = 2.02 O - 1 x 16.0 = 16.0 ------ 18.02 = amu

Group - vertical column of the periodic table.
Period - horizontal row of the periodic table.

Group 1 - Alkali metals
Group 2 - Alkaline Earth metals
Group 11 - Coinage metals
Group 17 - Halogens
Group 18 - Noble gases

Metals - left side of the dark, zig-zag line
Nonmetals - right side of the dark, zig-zag line
Metalloids - those elements that border the line that separates metals from nonmetals - have properties of both metals and nonmetals.

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p6 6s2 4f14 5d10 6p6 7s6 5f14 6d10 7p6 6f14

  1. Identify the number of electrons the element has.
  2. Fill each subshell completely until there are no more electrons needed.
  3. Do not fill a subshell if there are not enough electrons in that subshell

Oxygen -- 8 electrons

1s2 2s2 2p4 = electron configuration

Note--there are only 4 electrons in the last subshell because only 4 are needed, not a full 6.

Orbital Notation

  • Shows the rotation of the electrons within the subshell's orbital.

    Oxygen -- 8 electrons

    ↑↓      ↑↓       ↑↓   ↑    ↑
    ___    ___      ___  ___  ___
    1s2     2s2      2p4

Test Review
Test on

  • List the 4 postulates of Dalton's Atomic Theory
  • Identify the 3 main subatomic particles of atoms and their characteristics.
  • Know the difference between the atomic number and the mass number of an element.
  • Calculate the number of neutrons for a particular element.
  • Calculate the amu of different compounds.
  • Identify the difference between how Dmitri Mendeleev and Henry Moseley arranged the periodic table of elements.
  • Label a block from the periodic table - atomic number, chemical symbol, element name, mass number, and electron configuration.
  • Explain the difference between a period and a group.
  • Be able to label a blank periodic table with the following: alkali metals, alkaline earth metals, coinage metals, halogens, noble gases, transition metals, inner transition metals, lanthanide series, actinide series, nonmetals, and metals.
  • Give 4 characteristics of metals and nonmetals.
  • Draw the electron configuration and orbital notation for different elements.