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# Periodic Table of Elements

The periodic table of elements, simply called a Periodic Table, is a systematic arrangement of 118 known chemical elements. These chemical elements are organized in order of increasing atomic number, or the number of protons in an atom’s nucleus, which typically corresponds with increasing atomic mass, from left to right and top to bottom. The horizontal rows from left to right are called periods while the vertical columns from top to bottom are called groups in a periodic table.

Various scientists took part in the development of the Periodic table. John Newland, Mendeleev, and Moseley have a significant contribution to the History of Periodic Table that leads to the evolution of the periodic table to the Modern periodic table. The modern periodic table is based on the modern periodic law given by English Physicist Henry Moseley. When the chemical elements are arranged in such a recurring pattern follow a periodic trend that elements in the same column or group have similar properties.

## What is the Periodic Table?

A periodic table is a tabular representation in which all the known chemical elements are arranged in horizontal rows called periods and vertical columns called groups based on their atomic number and atomic structure respectively.

The periodic table is an essential aspect of Chemistry because it is an arrangement of all the known elements and therefore provides information about elements and their relation with one another in one easy-to-use reference. For example properties of particular elements such as their mass, electron number, electron configuration, and their unique chemical properties.

## Classification of Elements in the Periodic Table

The 118 elements are arranged in 7 periods and 18 groups as shown below. Further, the elements are divided into different blocks.

• s-block elements: The first and the second group elements that have the last electron filled in the s-subshell are called s-block elements. The elements included in the s-block are Alkali metals and Alkaline Earth Metals
• p-block elements: The elements included in groups 13 to 17 are p-block elements. These elements have the last electron filled in their p-subshell. The elements included in this block from different groups are termed as Boron Family (Group 13), Carbon Family (Group 14), Nitrogen Family (Group 15), Oxygen Family (Group 16), and Fluorine Family (Group 17).
• d-block elements: The elements present in groups 3 to 12 are d-block elements. These elements have the last electron filled in their d-subshell. d-block elements are also called transition elements as they have partially filled d-orbitals in their ground state.
• f-block elements: These elements have the last electron filled in their f-subshell. Such elements are present in Lanthanides and Actinides groups.

## Periodic Table of Elements List

Here is the table representing 118 elements of the periodic table. The elements listed are arranged according to the increasing order of atomic number and their respective atomic weight, symbols, density, and electronegativity.

## Mendeleev Periodic Table of Elements

Russian scientist Dmitri Ivanovich Mendeléev made the most significant contribution to the early creation of the periodic table. The Mendeleev periodic table was the most important of many periodic tables like the Newlands Octave Law that was rejected in 1869.

In order to represent similarities and trends in the behavior of elements, Mendeleev developed the periodic table, which is an arrangement of elements in an increasing atomic mass order in tabular form.

According to Mendeleev’s Periodic Table, elements were arranged as per their fundamental property, atomic mass, and chemical characteristics. Only 63 elements were known at the time of Mendeleev’s work. In the Mendeleev periodic table, the horizontal row and vertical columns were referred to as groups and periods, respectively.

However, Mendeleev’s Periodic Table fails due to many flaws in it. Some of them are, that it failed to designate Hydrogen and Noble gases in it. Also, the increasing order of the atomic mass of the elements wasn’t regular throughout the table. Even, the discovery of isotopes violates the Mendeleev Periodic Law.

## Important Terms used in a Periodic Table

• Atomic Number: The number of protons that constitutes an element’s nucleus is called its Atomic Number (Z). e.g. Carbon contains 6 protons then, so its atomic number must be 6 only.
• Atomic Mass: It is defined as the average mass of the atoms of an element. It is measured on the basis of the relative natural abundance of the isotopes of the element. Atomic mass is also termed Atomic Weight (A). It is measured in the atomic mass unit (amu).
• Period: The horizontal rows from left to right in a periodic table are called Periods. There are a total of 7 periods in the periodic table. The elements are arranged horizontally due to their similarities in properties, like the same atomic orbitals and so on.
• Group: The vertical columns from top to bottom in a periodic table are called Groups. There is a total of 18 groups in the periodic table. The elements are arranged vertically due to their similarities in properties, as they have the same number of valence electrons in them.
• Symbol of an Element: A symbol is a notion that is used to represent a chemical element using a letter or a combination of two to three letters. e.g. The chemical symbol of Carbon is C, while Fe is used for Iron and so on.

## FAQs on Periodic Table of Elements

Question 1: What are naturally occurring elements?

Naturally occurring elements are the elements that exists naturally and freely in nature. It is meant that first 92 elements in the periodic table occur naturally like Hydrogen, Carbon, Nitrogen, etc.

Question 2: What is the atomic number?

The number of protons that constitutes an element’s nucleus is called its Atomic Number (Z). e.g. Carbon contains 6 protons then, its atomic number must be 6 only.

Question 3: Can two different elements have the same atomic number?

The number of neutrons in an atom from two different elements can be similar, but the number of protons will never be same. Each element has a specific number of protons, which corresponds to the number of atoms.

Question 4: How do we calculate atomic mass?