Introduction to the Periodic Table

what's covered

In this lesson, you will be introduced to the periodic table of elements. Specifically, this lesson covers:

Table of Contents 1. The Periodic Table 2. Understanding the Parts of the Periodic Table

1. The Periodic Table

As early chemists worked to purify ores and discovered more elements, they realized that various elements could be grouped together by their similar chemical behaviors. One such grouping includes lithium (Li), sodium (Na), and potassium (K); these elements all are shiny, conduct heat and electricity well, and have similar chemical properties. A second grouping includes calcium (Ca), strontium (Sr), and barium (Ba), which also are appear shiny, conduct heat and electricity well, and share chemical properties. However, the specific properties of these two groupings are notably different from each other.

EXAMPLE

For example, Li, Na, and K are much more reactive than are Ca, Sr, and Ba; Li, Na, and K form compounds with oxygen in a ratio of two of their atoms to one oxygen atom, whereas Ca, Sr, and Ba form compounds with one of their atoms to one oxygen atom. Fluorine (F), chlorine (Cl), bromine (Br), and iodine (I) also exhibit similar properties to each other, but these properties are drastically different from those of any of the elements above.

people to know

Dimitri Mendeleev in Russia (1869) and Lothar Meyer in Germany (1870) independently recognized that there was a periodic relationship among the properties of the elements known at that time. Both published tables with the elements arranged according to increasing atomic mass. But Mendeleev went one step further than Meyer: He used his table to predict the existence of elements that would have properties similar to aluminum and silicon but were yet unknown.

The discoveries of gallium (1875) and germanium (1886) provided great support for Mendeleev’s work. Although Mendeleev and Meyer had a long dispute over priority, Mendeleev’s contributions to the development of the periodic table are now more widely recognized.

2. Understanding the Parts of the Periodic Table

key concept

By the twentieth century, it became apparent that the periodic relationship involved atomic numbers rather than atomic masses. The modern statement of this relationship, the periodic law, is as follows: the properties of the elements are periodic functions of their atomic numbers. A modern periodic table arranges the elements in increasing order of their atomic numbers and groups atoms with similar properties in the same vertical column.

Each box represents an element and contains its atomic number, symbol, average atomic mass, and (sometimes) name. The elements are arranged in seven horizontal rows, called periods or series, and 18 vertical columns, called groups.

Follow this link to WebElements to view an accessible version of the periodic table of elements (Winter, 2021).

Many elements differ dramatically in their chemical and physical properties, but some elements are similar in their behaviors. For example, many elements appear shiny, are malleable (able to be deformed without breaking) and ductile (can be drawn into wires), and conduct heat and electricity well. Other elements are not shiny, malleable, or ductile, and are poor conductors of heat and electricity.

We can sort the elements into large classes with common properties: metals (elements that are shiny, malleable, good conductors of heat and electricity—shaded yellow); nonmetals (elements that appear dull, poor conductors of heat and electricity—shaded green); and metalloids (elements that conduct heat and electricity moderately well and possess some properties of metals and some properties of nonmetals—shaded purple).

The elements can also be classified into the main-group elements in the columns labeled 1, 2, and 13–18; and the transition metals in the columns labeled 3–12.

The elements can be subdivided further by more specific properties, such as the composition of the compounds they form. For example, the elements in group 1 (the first column) form compounds that consist of one atom of the element and one atom of hydrogen. These elements (except hydrogen) are known as alkali metals, and they all have similar chemical properties.

The elements in group 2 (the second column) form compounds consisting of one atom of the element and two atoms of hydrogen: These are called alkaline earth metals, with similar properties among members of that group.

Other groups with specific names are the pnictogens (group 15), chalcogens (group 16), halogens (group 17), and the noble gases (group 18, also known as inert gases).

The groups can also be referred to by the first element of the group: For example, the chalcogens can be called the oxygen group or oxygen family. Hydrogen is a unique, nonmetallic element with properties similar to both group 1 and group 17 elements. For that reason, hydrogen may be shown at the top of both groups, or by itself.

terms to know

Periodic Law

The periodic relationship involving atomic numbers and states that the properties of the elements are periodic functions of their atomic numbers.

Periodic Table

An arrangement of the elements in increasing order of their atomic numbers and groups atoms with similar properties in the same vertical column.

Metals

Elements that are shiny, malleable, good conductors of heat and electricity—shaded yellow on the periodic table.

Nonmetals

Elements that appear dull, poor conductors of heat and electricity and are shaded green on the periodic table.

Metalloids

Elements that conduct heat and electricity moderately well, and possess some properties of metals and some properties of nonmetals, and are shaded purple on the periodic table.

Main-Group Elements (or Representative Elements)

The elements in columns labeled 1, 2, and 13–18, in the periodic table.

Transition Metals

The elements in columns labeled 3–12, in the periodic table

Alkali Metals

Elements, except hydrogen, in group 1 (the first column) form compounds that consist of one atom of the element and one atom of hydrogen.

Alkaline Earth Metals

The elements in group 2 (the second column) form compounds consisting of one atom of the element and two atoms of hydrogen.

REFERENCES

The periodic table of the elements by WebElements.Winter, M. (2021). Retrieved August 7, 2022 from The periodic table of the elements by WebElements.https://webelements.com/.