The periodic table ranks the elements in the most logical and easy-to-read manner based on their physical and chemical characteristics. In the modern periodic table, elements are listed based on their atomic number, which is the most common basis for their categorization and place on the table.
Dmitri Mendeleev, a Russian scientist, first designed the periodic table in 1869. Scientists worldwide adopted it as it showed a new way to represent and classify the elements (1). Furthermore, it is easy to read and can be used to teach chemistry using a visual aid. In this post, we describe how the periodic table is laid out, the logic behind it, and how to read it.
Why Is It Called The Periodic Table?
The elements in the periodic table are arranged in rows and columns. There are 18 columns known as groups and seven rows called periods. The periodic table gets its name from the seven periods (2).
Each element is placed along with other elements sharing the same characteristics, such as non-metal and noble gas. These elements are considered part of the same group. Elements in a group share similar characteristics, including the way they react to other elements.
The Periodic Table
How To Read The Periodic Table?
There are various ways in which the elements in the periodic table are placed and characterized. An element can be considered a part of a row and column with further sub-classifications across rows, columns, or the table. Therefore, the interpretations are vast and could vary based on one’s purpose. Below we explain the basic forms of classification of elements in the periodic table.
1. Fundamental division
The periodic table has the following fundamental attributes.
- There are seven rows or periods. These elements share physical properties, such as malleability and conductivity. Two rows of elements from the atomic number 57 to 71 (lanthanides) and 89 to 103 (actinides) are usually grouped below the main table.
- There are 18 columns or groups. These groups share similar atomic structures and characteristics, such as valency (combining capacity of the atoms).
The elements in the periodic table can be classified into the following three basic types or sub-groups.
- Metals: These elements share similar characteristics of melting point, malleability (flexibility), and conductivity (transmission of electricity and heat).
- Non-metals: Non-metal elements are typically non-conductors or poor conductors of heat and electricity. They are not malleable and lack the characteristic shine or luster of metals.
- Metalloids: These are also called semi-metals in chemistry. Metalloid elements have characteristics that lie in between metals and non-metals. For instance, metalloids could be shiny like metals but could be poor conductors of heat like non-metals. Some metalloids could be malleable like metals, while others could have poor malleability like non-metals.
3. Column groups
The elements can also be read as part of a group (column). Elements in each column usually share similar characteristics. Below are the names of various columns.
- Column 1: Hydrogen and alkali metals
- Column 2: Alkaline earth metals
- Columns 3 to 12: Transition metals
- Columns 13 to 16: Post-transition metals, metalloids, and non-metals
- Column 17: Halogens
- Column 18: Noble gases
The columns 3 to 16 also consist of lanthanides, also known as rare-earth elements, and actinides. The properties of these elements differ from the rest. Thus, they are placed at the bottom of the periodic table.
4. Atomic number, atomic mass, and atomic weight
- Atomic number: It is the number of protons (positively charged particles) present in the nucleus of an element’s atom. It is often represented by the letter Z.
- Atomic mass: It is the number of protons and neutrons (neutrally charged particles) present in the nucleus of an element’s atom. It is often represented by the letter A.
- Atomic weight: An element could have multiple isotopes, which are different forms of the element with the same atomic number (same number of protons) but different number of neutrons. The atomic weight is the average of the atomic masses of all the isotopes of the element.
The following interpretations and characteristics of elements can be observed based on their atomic number, atomic mass, and atomic weight.
- Each element will typically contain one more proton than the one before it. For example, Helium (He) has an atomic number of 2, which is 1 more than the previous element Hydrogen (H). Therefore, the atomic number (the number of protons) will increase as you go down the table.
- Since the number of protons increases, atomic mass and weight increase as you go down a period or across a group, with some notable exceptions.
- Groups of elements typically have the same color scheme and will share many physical properties.
- Some element groups could display changes in physical properties as their atomic masses change. For instance, noble gases tend to become denser as their atomic mass increases.
- The atomic number (number of protons) of an element will always remain the same. However, there could be several undiscovered isotopes of the element. Therefore, the atomic weight could be subject to change, and the one mentioned on the periodic table is generally considered provisional.
Facts About The Periodic Table For Kids
- The periodic table was designed to accommodate elements that were discovered later. New elements can be categorized and positioned in the existing periodic table. In fact, many elements present in the modern periodic table were not part of the original periodic table in 1869.
- The periodic table has many elements and their elemental symbols contain almost every letter in the alphabet except the letter “J.” New elements are still being discovered, and it is quite likely “J” could be assigned as an elemental symbol.
- As of 2021, there are 118 elements in the modern periodic table. 94 elements are naturally occurring elements found on Earth. 24 elements are human-made and are known as synthetic elements.
- The most recently added elements to the periodic table were Nihonium, Moscovium, Tennessine, and Oganesson. These elements were added in 2016 after a five-month review by the International Union of Pure and Applied Chemistry (IUPAC).
The periodic table is a catalog of elements and makes it easy to understand their properties. The table can make it simpler for one to determine the qualities of an element and its possible chemical interactions by looking at its position in the table. Understanding the fundamentals and regular practice can make it easier for children to love and appreciate the periodic table.
2. Periodic Table of Chemical Elements; American Chemical Society
3. Atomic Number and Atomic Mass; Radiation Emergency Medical Management
4. Periodic Table of Elements; Los Alamos National Laboratory
5. IUPAC is naming the four new elements nihonium, moscovium, tennessine, and oganesson; IUPAC
6. Jennifer Chu, An element that’s rare on Earth is found far, far away; Massachusetts Institute of Technology
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