What Are the Parts of the Periodic Table?

The periodic table of elements is the most important tool in chemistry. Knowing the parts of the periodic table and how to use the chart to predict element properties helps you get the most out of the table.

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 the element's arrangement have significance.

Each of the elements can be assigned to one of three broad categories of elements: metals, metalloids, and nonmetals.

Metals

Except for hydrogen, the elements on the left-hand side of the periodic table are metals. Hydrogen acts as a metal, too, in its solid state, but the element is a gas at ordinary temperatures and pressures and doesn't 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 periodic table body are metals. Specifically, they're a collection of transition metals called lanthanides and actinides, or 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)

A zig-zag line toward the right side of the periodic table acts as a border, of sorts, between metals and nonmetals. Elements on either side of this line exhibit some properties of metals and some of nonmetals (these elements are metalloids, also called semimetals).

Metalloids have variable properties, but often they:

• 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 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 periodic table's arrangement organizes elements with related properties. Groups and periods are two general categories.

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 bond with each other to form compounds.

Ionic Bonds
Ionic bonds form between atoms with extremely different electronegativity values. Ionic compounds form crystal lattices containing positively charged cations 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, a type of bond that 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. The metals readily conduct electricity because the electrons can move freely.