What Are the Parts of the Periodic Table?

Periodic Table Organization and Trends

The periodic table may be broken into 3 main parts: metals, semimetals, and nonmetals.
The periodic table may be broken into 3 main parts: metals, semimetals, and nonmetals. Todd Helmenstine

The periodic table of elements is the most important tool used in chemistry. To get the most out of the table, it helps to know the parts of the periodic table and how to use the chart to predict element properties.

3 Main Parts of the Periodic Table

The periodic table lists the chemical elements in order of increasing atomic number, which is the number of protons in each atom of an element. The shape of the table and way the elements are arranged has significance.

Each of the elements can be assigned to one of three broad categories of elements:

Metals

With the exception of hydrogen, the elements on the left-hand side of the periodic table are metals. Actually, hydrogen acts as a metal, too, in its solid state, but the element is a gas at ordinary temperatures and pressures and does not display metallic character under these conditions. Metal properties include:

  • metallic luster
  • high electrical and thermal conductivity
  • usual hard solids (mercury is liquid)
  • usually ductile (capable of being drawn into a wire) and malleable (capable of being hammered into thin sheets)
  • most have high melting points
  • readily lose electrons (low electron affinity)
  • low ionization energies

The two rows of elements below the body of the periodic table are metals. Specifically, they are a collection of transition metals that are called the lanthanides and actinides or the rare earth metals.

These elements are located below the table because there wasn't a practical way to insert them into the transition metal section without making the table look strange.

Metalloids (or Semimetals)

There is a zig-zag line toward the right side of the periodic table that acts as a sort of border between metals and nonmetals.

Elements on either side of this line exhibit some properties of metals and some of the nonmetals. These elements are the metalloids or semimetals. Metalloids have variable properties, but often:

  • metalloids have multiple forms or allotropes
  • can be made to conduct electricity under special conditions (semiconductors)

Nonmetals

The elements on the right-hand side of the periodic table are the nonmetals. Nonmetals properties are:

  • usually poor conductors of heat and electricity
  • often liquids or gases at room temperature and pressure
  • lack metallic luster
  • readily gain electrons (high electron affinity)
  • high ionization energy

Periods and Groups in the Periodic Table

The arrangement of the periodic table organizes elements with related properties. Two general categories are groups and periods:

Element Groups
Groups are the columns of the table. Atoms of elements within a group have the same number of valence electrons. These elements share many similar properties and tend to act the same way as each other in chemical reactions.

Element Periods
The rows in the periodic table are called periods. Atoms of these elements all share the same highest electron energy level.

Chemical Bonding To Form Compounds

You can use the organization of elements in the periodic table to predict how elements will form bonds with each other to form compounds.

Ionic Bonds
Ionic bonds form between atoms with very different electronegativity values. Ionic compounds form crystal lattices containing positively charged cation and negatively-charged anions. Ionic bonds form between metals and nonmetals. Because ions are fixed in place in a lattice, ionic solids don't conduct electricity. However, the charged particles move freely when ionic compounds are dissolved in water, forming conductive electrolytes.

Covalent Bonds
Atoms share electrons in covalent bonds. This type of bond forms between nonmetal atoms. Remember hydrogen is also considered a nonmetal, so its compounds formed with other nonmetals have covalent bonds.

Metallic Bonds
Metals also bond to other metals to share valence electrons in what becomes an electron sea surrounding all the affected atoms.

Atoms of different metals form alloys, which have distinct properties from their component elements. Because the electrons can move freely, metals readily conduct electricity.