The Periodic Table of Elements

***Except Aluminum (not considered a metalloid)

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:

Atomic Number

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

Atomic mass - Atomic Number = Number of Neutrons

Atomic Mass Unit (amu)

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.


An Element of Interest
Periodic Table of Elements