How to Read the Periodic Table

Core Concepts:

In this tutorial, you will learn how to read the periodic table. In addition, you will learn about the different properties of the elemental groups, periods, and families. If you enjoy this article, be sure to check out our others!

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  • Elements: A pure substance composed of a single atom.
  • Groups: The vertical column of the periodic table that signifies the number of valence electrons in an element.
  • Periods: The horizontal rows in the periodic table that signify the number of electron shells in an element.
  • Families: Elements that have the same number of valence electrons and therefore similar properties.

The Periodic Table and the Periodic Trends

The periodic table is organized into groups (vertical columns), periods (horizontal rows), and families (groups of elements that are similar). Elements in the same group have the same number of valence electrons. Meanwhile, elements in the same period have the same number of occupied electron shells. In 1869 Russian chemist Dmitri Mendeleev noticed there existed an innate pattern of organization for the chemical elements. From this deduction, he formed the periodic table. It is important to note how the location of elements on this table tells us about their properties. A quick way to understand an element’s chemical and physical properties is to know the periodic trends. These trends tell you where the highest and lowest types of properties are concentrated on the periodic table. For a more in-depth explanation of periodic trends, click here.

Periods on the Periodic Table

Periods are the horizontal rows of the periodic table. There are seven periods total and each element in a period has the same number of atomic orbitals. The top period, which contains hydrogen and helium, has only two orbitals. As you go down the rows, the number of orbitals increases. Below is a table to help visuals the periodic number and the corresponding orbitals.

Period NumberNumber of OrbitalsNumber of Elements

Groups of the Periodic Table

As previously mentioned, the vertical columns on the periodic table are called “groups”. There is eighteen total and each group contains elements with the same number of valence electrons. The number of valence electrons present dictates the properties of an element. The reason for this is that the valence electrons, which are the electrons in the outermost shell, are the ones taking part in chemical reactions. These electrons are either donating, accepting, or sharing. Moreover, the more filled the valence shell is, the more stable the element. The first group is the least stable as it only has one valence electron. Meanwhile, group eighteen is the most stable as these elements have a full valence shell (eight valence electrons). Below is a table relating the group numbers to the number of valence electrons.

Group NumberNumber of Valence Electrons

Families of the Periodic Table

On the periodic table, there are families which are groups of elements with similar properties. These families are alkali metals, alkaline earth metals, transition metals, post-transition metals, metalloids, halogens, noble metals, and noble gases. Many of these families belong to a single group. However, not all of the families overlap with periodic table groups. For example, the transition metals contain all elements from group three to group twelve. Below is a periodic table where displaying the location of each family.


The Alkali Metals (Group 1)

The alkali metals consist of all of the elements in group one with the exception of hydrogen. These elements are extremely reactive and for this reason, are usually found in compounds. In addition, they are water-sensitive (they react violently with water), so they must be stored in oil. The most reactive alkali metal is francium and it decreases as you go up the group. This means lithium is the least reactive. Physically, the alkali metal family is silvery, white, and light. They also have low melting and low boiling points.

The Alkaline Earth Metals (Group 2)

The alkaline earth metals are the second most reactive family on the periodic table (following behind the alkali metals). Moreover, they are strong reducing agents which means they donate electrons in chemical reactions. They are also good thermal and electrical conductors. Physically, they have low density, low melting point, and a low boiling point.

Rare Earth Metals: Lanthanides

Lanthanides are a family of rare earth metals that contain one valence electron in the 5d shell. They are highly reactive and a strong reducing agent in reactions. Furthermore, they are a silvery-bright metal and are relatively soft. They also have both high melting points and high boiling points.

Rare Earth Metals: Actinides

Actinides are another family of rare earth metals. Like the lanthanides, these elements are highly reactive. They also have high electropositivity and are radioactive. Additionally, these elements contain paramagnetic, pyromorphic, and allotropic properties. Physically, they are very similar to lanthanides. They are silvery metals that are soft, malleable, and ductile.

The Transition Metals (Groups 3-12)

The transition metals typically form two or more oxidation states. They have low ionization energies and high conductivity. In addition, they have high melting points, high boiling points, and high conductivity. Physically they are both metallic and malleable.

Post Transition Metal

The post transition metals are located in between the transiion metals and the metalloids. At standard temperature, they are in a solid state of matter. They tend to have a high density as well as high conductivity. Physically they are malleable and ductile.

The Metalloids

The metalloids display properties of both metals and non-metals. For example, metals are good conductors and non-metals are poor conductors. This means metalloids are semiconductors (only conducts electricity at high temperatures.). Also, they are more brittle than metals but less brittle than non-metals. Physically they can be either shiny or dull and are typically ductile and malleable.

The Halogens (Group 17)

The name halogen means “salt formers” in greek. This is evident in nature as halogens interact with metals to form various salts. On another note, the halogens are a unique group of elements. They are the only periodic family that contains elements in the three states of matter at standard temperature. There are 6 halogens and they are located in group 17. These elements include fluorine (F), chlorine (Cl),  bromine (Br), iodine (I), and astatine (At). They are highly reactive, highly electronegative, and highly toxic non-metals.

Noble Metals

The noble metals consist of ruthenium (Ru), osmium (Os), rhodium (Rh), iridium (Ir), Pd, platinum (Pt), gold (Au), silver (Ag). Like the noble gases, they are inert due to having a complete valence shell. In addition, noble metals have catalytic tendencies. Also, they are very resistant to corrosion, tarnishing, and oxidation. Finally, like many of the other metals, they are soft and ductile.

Noble Gases (Group 18)

The noble gases, also called aerogens, are inert gases. They can be found in group eighteen on the periodic table. Likewise, this means they have a complete valence shell. For this reason, they are stable and relatively unreactive. Furthermore, the noble gases have low boiling points and low melting points. Physically they are colorless and have no smell.

Summary Table for Family Properties

Family TypeProperties
Alkali Metals– highly reactive
– water-sensitive
– Soft
– low density
– low melting point
– low boiling point
Alkaline Earth Metals– Strong reducing agents
– Silvery, shiny metal
– Good conductors
– Low density
– Low melting point
– Low boiling point
Transition Metals– 2 or more oxidation states
– Usually forms paramagnetic compounds
– Low ionization energies
– High melting point
– High boiling point
– High conductivity
– Metallic
– Malleable
Post Transition Metals– Solid at standard temperature
– Malleable
– Ductile
– High conductivity
– High density
Metalloids– Semi-conductors (conducts only at high temperatures)
– More brittle than metals but less brittle than non-metals
– Properties are a mix between metals and non-metals
– Shiny or dull
– Ductile and malleable
Lanthanides– 1 valence electron in 5d shell
– Highly reactive
– Strong reducing agent
– Silvery bright metal
– Relatively soft
– High melting points
– High boiling points
Actinides– Highly reactive
– High electropositivity
– Paramagnetic
– Pyromorphic
– Allotropic
– Radioactive
– Silvery metals
– Ductile
– Malleable
– Soft
Halogens– Highly reactive
– High electronegativity
– Non-metal
– Toxic
Noble Metals– Relatively unreactive
– Complete valence shell (8 valence electrons)
– Inert
– Catalytic
– Resistant to corrosion, tarnishing, and oxidation
– Soft and Ductile
Noble Gases– Relatively unreactive
– Complete valence shell (8 valence electrons)
– Low electronegativity
– Colorless and odorless
– gases under standard conditions
– Non-metal
– Low boiling point
– Low melting point
– Density increases as you go down

Further Reading

The Structure of an Atom

Periodic Trends Made Easy!

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