Atomic Numbers -The Periodic Table of Elements

Atomic Numbers

Atomic Numbers: Introduction

 The atomic numbers are the fundamental properties of an atom. The atomic number can be defined as the number of protons present in an atom. Isotopes also have a similar atomic number but with different numbers of neutrons. We might have come across discussions on the domain of nuclear energy and nuclear weapons. Radioactivity becomes an important and commonly used term in the news. The fundamental property of an atom is radioactivity. Radioactive atoms usually have unstable nuclei. They could release some atomic particles to increase its stability resulting in radiation during the process. Elements are found to come in connection with both nonradioactive and radioactive versions which differ in the quantity of neutrons content.

Isotopes are defined as different element versions. We can find radioactive isotopes in a very small quantity in nature. For example, the atmosphere contains carbon in a very small quantity as radioactive carbon-14. This is also found in fossils which allow palaeontologists to identify the age of such fossils. Every element contains atoms with a certain number of protons which in turn determines the actual atom. For example, the neutrons content can vary from one element to the other.

Isotopes are similar atoms with different numbers of neutrons. Together with the number of neutrons and protons usually, determine the mass number of an element. The mass number is the summation of the number of neutrons and protons. If anyone wants to calculate the number of neutrons in an atom, he or she can simply deduct the atomic number or the number of protons from the mass number.

The atomic mass can be defined as a property which is closely related to the mass number of an atom. The atomic mass of an individual atom is the total mass and it is fundamentally expressed in AMU or atomic mass units. A Periodic Table is highly essential for the chemist and students we can place the table where we need it in solving problems, mark up and get a new one printed. The periodic tables use accurate information and data for atomic number, name element, symbol, electron configuration, and atomic weight. Now our instant assignment experts will explain you the purpose of the periodic table with atomic numbers.

Purpose of periodic table
Purpose of periodic table

What are Periodic Table Atomic Numbers?

The Periodic Table can be considered as one of the most essential scientific documents which are developed in the form of a single table. It contains every kind of information related to chemical knowledge that human beings have imbibed since centuries. There are in total of 118 elements in the table that are arranged in terms of their atomic numbers and also according to the number of free electrons that are grouped according to the resemblances in their chemical properties.

We can say that all the matter that we observe in the universe is created by building blocks which are known as elements. The distinction between all these elements is possible with the help of atomic number. Each and every element has a unique atomic number that makes it possible to distinguish between several elements. An atom is made up of protons, electrons, and neutrons. The atomic number can be considered as a fundamental property of an atom. Each atom has a unique and distinct atomic number. The atomic number of an atom is denoted by the letter ‘Z’. The atomic number of a typical atom is represented by the total number of protons that make up the nucleus of the atom.

We may say that each atom of a particular element has the same number of protons and therefore, they possess exactly the same atomic number. Likewise, atoms belonging to diverse elements have specific atomic numbers that vary between all the elements. An atom of an element is electrically neutral because the number of protons and electrons within an atom are identical which makes the atom neutral electrically.

“Atomic Number = No. of Protons = No. of Electrons”

History of the Periodic Table

The history of the periodic table dates back to centuries. There have been quite a number of iterations in the table before the final one that we use today has been developed. The first version of the periodic table was an attempt made by Antoine Lavoisier in the year 1789 where he published a list containing 33 chemical elements. These elements were grouped into categories of earth, metals, non-metals, and gases.

Then, it was in the year 1829 that Johann Wolfgang tried to make some amendments to this table by undertaking an approach where he tried to observe the resemblances existing in the chemical properties of the triads of elements and then grouped them which gave rise to the Law of Triads. A number of revisions were made by the chemists to the periodic table yet, the current groupings of the elements were not achieved. Furthermore, it was in the year 1862 that Alexandre-Émile Béguyer de Chancourtois came up with a helix format of the periodic table. In this format, the elements have been arranged in the form of a spiral on a cylinder and it was an attempt to indicate the periodicity in the properties of the elements for the first time.

It is interesting to learn that Chancourtois indexed the elements in the table by enhancing the atomic weight and demonstrating that identical chemical properties were being reflected at regular intervals. But, unfortunately, his work did not receive adequate critical acclaim around the world. But, the globally accepted periodic table that we now know of was developed by Dmitri Mendeleev, a Russian scientist in the year 1871. The globally accepted periodic table that we consult today is composed of eight columns, each one consisting of elements with identical properties.

The columns are numbered from I to VIII and contain empty spaces for including undiscovered elements. Mendeleev’s prediction was right as more and more elements were being discovered by chemists that kept on filling the gaps in the periodic table. Now our experts from Online Assignment Help will tell you about the grouping method in the periodic table.

Grouping Method in the Periodic Table


 The modern periodic table consists of 18 vertical columns that are referred to as Groups. The total number of electrons existing in the outermost shell of an atom which is known as the Valence Shell is identical for all the elements under the same group. The group in the extreme left consists of the alkali metals and the group at the extreme right-hand side consists of noble gases. Elements that are located within the same column demonstrate identical chemical properties and they demonstrate periodicity when there is an enhancement in their atomic number.

Elements contained within the same group demonstrate patterns in their atomic radius, electronegativity and ionization energy. The numbering of the groups has been done from left to the right from 1 to 18. It is interesting to learn that the conventions in naming the groups varied between Europe and America. However, since the year 1988 when the IUPAC names were put into place, the usage of the old names was abandoned. The arrangement of the groups is done in such a manner that as one moves down a group the atomic radius is enhanced, there is a decrease in electronegativity, except for Group 11 and there is a decrease in ionization energy.


 The vertical rows existing within the periodic table are referred to as periods. Lanthanides and actinides within the f-block demonstrate enhanced resemblance within the same period as compared to within the same group. When we are moving from left to the right within a period there are certain occurrences such as a decrease in the atomic size due to the presence of a nuclear force that is extremely strong. There is an increase in ionization energy and also in electronegativity. Furthermore, there is an increase in the electron affinity, except the noble gases. 


The blocks in the periodic table are the different sections. The naming of each block is done on the basis of the letter contained in the outermost subshell in which an electron is present. The four blocks consist of the s- block consisting of alkali metals in Group 1 and alkaline earth metals in Group 2. The p-block containing the group numbers 13-18, inclusive of all the metalloids. Also, there is the d-block that contains the group numbers 3-12 and consists of the transition metals. The f-block contains the lanthanides and actinides but they do not have any group number.

Metals, Metalloids & Non-Metals

We can group the elements in terms of their chemical and physical properties and characteristics into the following:

  • Metals- The metals are the solids with high conductivity that form ionic compounds when mixed with different elements. The metals are subdivided into groups such as the Alkali Metals under Group 1, Alkaline Earth Metals under Group 2, Lanthanides and Actinides under f-block, and post-transition metals. We come to learn that metals develop into alloys when mixed with each other.
  • Non-metals- The non-metals are either coloured or colourless solids, liquids or gases which partake in covalent bonding along with several other elements. They are classified into several categories such as monatomic which are the inert non-metals, diatomic and polyatomic.
  • Metalloids- Metalloids have combined properties of metals and non-metals.

Periodic Table Types

Long Table

The long periodic table is generated by putting the f-block in between the d-block and the s-block. Here, in place of putting the rows at the bottom, and keeping them disconnected from the entire table. In this format of the table, it is easier to observe the trends and the enhancements of the atomic numbers. But, one of the major problems with this format of the table is that it is extremely difficult to print this version of the atomic table. Therefore, it is evident that the long format of the periodic table is developed according to the increasing order of atomic numbers.

The advantage of this form of the table is that it is possible to make accurate predictions of the properties of the various elements and the compounds. The limitations of the periodic table by Mendeleev do not exist in this long format of the periodic table as all the elements are ordered according to their increasing atomic numbers. So, we can say that the major characteristics of this form of the periodic table are that the elements that are placed under a group demonstrate identical chemical properties because of the configuration of the outer electron that is the identical number of valence electrons. This periodic table depicts the arrangement of the elements as per the modern periodic law, the presence of 18 vertical columns that are referred to as groups, presence of 7 horizontal rows referred to as periods and that the elements with identical outer electronic configuration possessing the same valence are placed under the same group.

Benfey’s Spiral Table

 This form of the periodic table is developed by Otto Theodor Benfey and in this table, the arrangement of the elements is done in the form of a continuous spiral which has hydrogen at the centre and the peninsulas are made up of the transition metals, lanthanides, and actinides. Some of the advantages of this form of the periodic table are that this table clearly shows the group names where the elements are located. This is a sharp contrast to the traditional periodic table where the names of the elements have to be memorized. Each of the colours represents one group of elements such as the Alkali Metals, Metalloids, and others.

This format of the periodic table also demonstrates the configuration of the electrons. Here, the Lanthanides and Actinides and the Transition Metals form distinct and diverse curves as they form the d-block and the f-block. Each of the spirals represents a particular period on the traditional periodic table. The division is the same as in the traditional periodic table. Furthermore, unlike the traditional periodic table, there are no gaps between the elements. However, there are certain distinct disadvantages of this form of the periodic table. We can determine them to be the fact that this table does not offer much insight about the element and at the same time, it does not give us the atomic mass and the atomic number. It is essential to learn that this table does not depict the electron configuration of all the elements, except for the elements in the f-block and the d-block. The table is a bit difficult to observe and understand without the atomic numbers around the spiral and also causes problems in understanding the organization of the periods.

To add to these limitations, are other drawbacks such as the lack of any information on the group each of the elements belongs to and the reason they are shaded in distinct and typical colours. The names that are located within the curves are difficult to keep track of along with the periods. The table only gives the names of certain groups of elements and last but not the least, all the elements within the table are continuous in nature so that we do not have to jump from one side to the other in the table like we have to do in the case of the traditional periodic table.

Janet’s Left Step Table

The left step periodic table has been introduced by Charles Janet in the year 1928. It is one of the most important alternatives to the functional depiction of the entire periodic system. Janet’s left-step table is built with an order where the energy levels of atom get filled as 1s, 2s, 2p, 3s, 3p, 4p and so on. It is not an obvious order but it is quite difficult to discover the basic regularity behind the list. The regularity is generally expressed by some star-like structures located at the bottom of the table. The table needs to be read in a normal reading manner from the top level to the bottom and from left to the right. This table depicts the energy levels of atoms. The energy levels successively fill the consecutive atomic numbers and directly develop the periodic table.

The particular electronic configuration or structure of a specific element can be read directly from the table. The simplified version of this table is not that well known because chemists use conventional tables more often.  This table has been read discovered by different people. It arranges elements on the basis of idealized orbital filling. In the traditional form of the periodic table, valence has been used. In the left-step table, Helium has been placed in group 2 instead of the group.  Group 1 and 2 which is represented in the S-block include 119 and 120 elements in the extended period of 8 they have been moved to the right-hand side of the table. From the table, we can see that the S-block has also been shifted upwards. All the elements which are placed in the S-block are now placed one row lower from that of the standard table. For example, the fourth row of the standard table has now become the fifth row in the left-step periodic table of Janet. The order is consistently maintained by an atomic number from 1 to 120. Assignment Help Canda will give you more information related to your science assignments.