Read the Periodic Table

The periodic table of elements lists the current 118 elements that have been discovered. There are several symbols and numbers that identify the differences in the elements, while the table’s structure organizes elements with similarities. You can read the periodic table using the guidelines below.

Steps

Sample Periodic Table

Doc:Periodic Table

Understanding the Structure

  1. View the periodic table as starting at the top left and ending at the end of the last row, near the bottom right. The table is structured from left to right in order of increasing atomic number. The atomic number is the number of protons in a single atom.
    • Not every row or column is complete. Although there may be breaks in the center, reading the table will continue from left to right. For instance, Hydrogen has an atomic number of 1 and it is in the top left. Helium has an atomic number of 2 and it is in the top right.
    • Elements 57 through 102 are usually pictured as a subset at the bottom right of the table. These are the “rare earth elements.”
  2. Find a “group” of elements in each column of the table. There are 18 columns.
    • Use the term “reading down a group” to read from top to bottom.
    • Numbering will usually be above the columns; however, it may appear below other groupings, such as metal.
    • The numbering used on the periodic table will differ greatly. They can be Roman (IA), Arabic (1A), or numbers 1 through 18.
    • Hydrogen may be placed in the halogen family and the alkali metal family, or both.
  3. Find a “period” of elements in each row of the table. There are 7 periods. Use the phrase “reading across a period” to read from left to right.
    • The periods are usually numbered 1 through 7 on the left hand side of the table.
    • Each period is bigger than the last. This is associated with increasing energy levels of atoms on the periodic table.
  4. Understand additional grouping according to metal, semi-metal and non-metal. The colors will vary greatly.
    • Metals are shaded one color. However, hydrogen is usually shaded and grouped with the non-metals. Metals have luster, are usually solid at room temperature, conduct heat and electricity and they are malleable and ductile.
    • Non-metals are shaded together. They are the elements C-6 to Rn-86, including H-1 (Hydrogen). They do not have luster, conduct heat or electricity and are not malleable. They are usually gasses at room temperature and can be solid, gas or liquid.
    • Semi-metals/metalloids are usually shaded purple or green, as a combination of the other 2 colors. The line is a diagonal, stretching from elements B-5 to At-85. They have some properties of metals and some of non-metals. [1]
  5. Consider that elements are also sometimes listed in families. These are alkali metals (1A), alkaline earth metals (2A), halogens (7A), noble gases (8A) and Carbons (4A).
    • The numbering can be Roman, Arabic or standard numbers.

Reading the Symbol and Name

  1. Read the symbol first. It is a 1 to 2-letter combination that is used as a standard across different languages.
    • The symbol can be derived from the Latin name of the element or the widely accepted common name.
    • In many cases, the symbol follows the English name closely, such as Helium, which is “He.” However, it is not a rule to base a chemistry lesson upon. For example, Iron is “Fe.” For this reason, the symbol/name combination is usually memorized for quick reference. [2]
  2. Look at the common name. This will appear just below the symbol. It will change depending upon what language the periodic table is written in.

Reading the Atomic Number

  1. Read the periodic table according to the atomic number at the top center or top left of each element’s box. As stated before, it moves from top left to bottom right. Knowing the atomic number is the fastest way to locate more information about the element.
  2. Understand that the atomic number is the number of protons in the nucleus of a single atom of the element.
  3. Know that adding or removing protons would create a different element. [3]
  4. Finding out the number of protons in an atom is also finding out the number of electrons. Atoms have equal numbers of electrons and protons.
    • Keep in mind that there is an exception to this rule. If the atom loses or gains electrons, it is an electrically charged ion.
    • If there is a plus next to the element’s symbol, it indicates it is positively charged. With a minus symbol, it is negatively charged.
    • If there is no plus or minus symbol, and your chemistry problem does not consider ions, the protons and electrons are likely equal.

Reading the Atomic Weight

  1. Find the atomic weight. This is the number below the common name of the element.
    • Although it may appear as though the atomic weight increases in number from top left to bottom right, this is not true in all cases.
  2. Understand that most elements will be listed with decimals. The atomic weight is the total of the particles in the nucleus; however, it is a weighted average of different isotopes.
  3. Use the atomic weight to find the number of neutrons in a single atom. Round the atomic weight to the nearest whole number, called the mass number. Then, subtract the number of protons from the mass number to get the number of neutrons. [4]
    • For example, iron’s atomic weight is 55.847, so its mass number is 56. It has 26 protons. 56 (mass number) minus 26 (protons) is 30. There are usually 30 neutrons in a single atom of iron.
    • Changing the number of neutron in an atom creates isotopes, which are heavier or lighter versions of the atom.

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Sources and Citations

  1. ↑ http://www.csun.edu/~psk17793/G%20Chemistry/reading_the_periodic_table.htm
  2. ↑ http://www.sparknotes.com/chemistry/fundamentals/periodictable/section2.rhtml
  3. ↑ http://education.jlab.org/qa/pen_number.html
  4. ↑ http://www.classzone.com/books/earth_science/terc/content/investigations/es0501/es0501page06.cfm
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