How to Use a Periodic Table of Elements

Periodic Table Organization

The periodic table contains informative cells for each element arranged by increasing atomic number and chemical properties. Each element's cell typically contains lots of important information about that element.

Element symbols are abbreviations of the element's name. In some cases, the abbreviation comes from the element's Latin name. Each symbol is either one or two letters in length. Usually, the symbol is an abbreviation of the element name, but some symbols refer to older names of the elements (for example, the symbol for silver is Ag, which refers to its old name, argentum).

The modern periodic table is organized in order of increasing atomic number. The atomic number is how many protons an atom of that element contains. The number of protons is the deciding factor when distinguishing one element from another. Variation in the number of electrons or neutrons does not change the type of element. Changing number of electrons produces ions while changing the number of neutrons produces isotopes.

The element's atomic mass in atomic mass units is a weighted average mass of the element's isotopes. Sometimes a periodic table cites a single value for atomic weight. Other tables include two numbers, which represent a range of values. When a range is given, it's because the abundance of isotopes varies from one sampling location to another. Mendeleev's original periodic table organized elements in order of increasing atomic mass or weight.

The vertical columns are called groups. Each element in a group has the same number of valence electrons and typically behave in a similar manner when bonding with other elements. The horizontal rows are called periods. Each period indicates the highest energy level the electrons of that element occupies at its ground state. The bottom two rows—the lanthanides and actinides—all belong to the 3B group, and are listed separately.

Many periodic tables include the element's name to help those who may not remember all the symbols for elements. Many periodic tables identify element types using different colors for different element types. These include the alkali metals, alkaline earths, basic metals, semimetals, and transition metals.

Periodic Table Trends

The periodic table is organized to showcase the different trends (periodicity).

• Atomic Radius (half the distance between the center of two atoms just touching each other)
  • increases moving top to bottom down the table
  • decreases moving left to right across the table
• Ionization Energy (energy required to remove an electron from the atom)
  • decreases moving top to bottom
  • increases moving left to right
• Electronegativity (measure of ability to form a chemical bond)
  • decreases moving top to bottom
  • increases moving left to right

Electron Affinity

The ability to accept an electron, electron affinity can be predicted based on element groups. Noble gases (like argon and neon) have an electron affinity near zero and tend not to accept electrons. Halogens (like chlorine and iodine) have high electron affinities. Most other element groups have electron affinities lower than that of the halogens, but greater than the noble gases.

Most of the elements are metals. Metals tend to be good electrical and thermal conductors, hard, and shiny. Nonmetals are clustered in the upper right hand section of the periodic table. The exception is hydrogen, which is on the top left of the table.

A good periodic table is a great tool for solving chemistry problems. You can use an online periodic table or print your own. Once you feel comfortable with the parts of the periodic table, quiz yourself to see how well you can read it.