How to Use a Periodic Table

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How to Use a Periodic Table

This periodic table wallpaper has element names, atomic numbers, atomic weight and more info.
A periodic table of the elements typically provides the element name, atomic number, symbol, and atomic weight. The colors denote the element groups. Todd Helmenstine

The periodic table of the elements contains a wide variety of information. Most tables list element symbols, atomic number, and atomic mass at a minimum. The periodic table is organized so you can see trends in element properties at a glance. Here is how to use a periodic table to gather information about the elements.

The periodic table contains informative cells for each element arranged by increasing atomic number and chemical properties. Each element's cell typically contains:

  • The element's symbol. Symbols are the 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 (e.g., The symbol for silver is Ag, which refers to the old name argentum.)
  • The element's atomic number. This number is the number of protons an atom of this 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 modern periodic table is organized in order of increasing atomic number.
  • The element's atomic mass in atomic mass units. This number is a weighted average mass of the element's isotopes. Mendeleev's original periodic table organized elements in order of increasing atomic mass or weight.
  • The element's name. Many periodic tables will include the name to help those who may not remember all the symbols for 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 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 bottom two rows, the lanthanides and actinides all belong to the 3B group and are listed separately.

Many periodic tables identify element types using different colors for different element types. These include the alkali metals, alkaline earths, basic metals, semimetals, transition metals, nonmetals, lanthanides, actinides, halogens and noble gases.

Periodic Table Trends

The periodic table is organized to showcase the following 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 (ability to accept an electron)

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

A good periodic table is a great tool for solving chemistry problems. You can use an online periodic table or print your own.

When you feel comfortable with the parts of the periodic table, take a quick 10-question quiz to test yourself on how well you can use the table.