What is a Periodic Table? – Definition, Elements, Groups

Do you know how many elements are available on our earth? And do you know how these elements are categorized into different groups? Knowing answers to these questions is very important while studying chemistry, which is solely based on the periodic table.  This atomic table of elements form a crucial study in chemistry forming a crucial tabular array defining and determining several other related branches of study.

Contents of the Article

And to help you out, we have put together a detailed guide to  

  • Periodic Table (understanding as the atomic table of elements)
  • Classification of All Elements in Modern Periodic Table
  • Different Groups in the Periodic Table
  • Elements of Periodic Table with Number
  • History of the periodic table
  • Periodicity of properties of elements

In this article, let us address the above contents, understanding the atomic table of elements in a broader sense

What is a Periodic Table?

What is Periodic Table

Let us first begin with the understanding of the periodic table. Before we get into the topic, let us first understand the History of the Periodic Table. In the year 1869, a Russian Scientist started categorizing available elements into groups and categories based on their atomic numbers and chemical formulas, as well as common similarities between elements, which are called Periodic Trends. However, at first, it was hard to organize elements into different groups; thus, it took rearranging multiple times. And over the years, this table has been labeled as a Periodic Table or the atomic table of elements.

In 1869, Mendeleyev’s periodic table covered 17 columns, with two almost complete periods (sequences) of elements. This ranged from potassium to bromine and rubidium to iodine and followed two partial periods of seven elements each (lithium to fluorine and sodium to chlorine). This is in turn followed by three incomplete periods.

Back in 1871 Mendeleyev presented a paper that stood as an improved and altered pattern, with a 17-group table. The major enhancement was the exact positioning of 17 elements, in a way altered positioning. He came up with a table of eight columns that was derived by fragmenting every long period into a period of seven, an eighth group containing the three central elements (such as iron, cobalt, nickel; Mendeleyev also included copper, and did not categorize it in Group I), and a second period of seven. The first and second periods of seven were later differentiated through using of the letters “a” and “b” attached to the group symbols, which were the Roman numerals.

Short-period form of Periodic system of elements, 1930

This was the era when thorium (90), protactinium (91), and uranium (92) did not get clarity on whether they were part of the actinide series. They used to be categorized under groups IVa, Va, and VIa, respectively. This was because they exhibited certain common features to those on hafnium (72), tantalum (73), and tungsten (74).

Post discovery of the noble gases helium, neon, argon, krypton, radon, and xenon by Lord Rayleigh (John William Strutt) and Sir William Ramsay in 1894, Mendeleyev along with others recommended the addition of a new “zero” group to the atomic table of elements, that can accommodate them. The “short-period” form of the periodic table, with Groups 0, I, II,…VIII, attained prominence and popularity, staying in relevance almost until 1930.

Inspired by previous models of T. Bayley, J. Thomsen conceived a new table in 1895. This was more determined by the electronic structure of atoms proposed by Niels Bohr in 1922. The table constituted periods of increasing length between the noble gases. The table contained a period of 2 elements, two of 8 elements, two of 18 elements, one of 32 elements, and an incomplete period. The elements in each period were linked by tie lines with one or more elements in the following period. The major gap found in this table was that it the period of 32 elements occupied excess space. Also, tracing a sequence of closely similar elements was found to be challenging.

Classification of Elements

All the elements in the Periodic Table, as stated above, are classified into multiple categories, such as,  

  • Metals 
  • Non-Metals 
  • Metalloids 
  • Noble Gases 


The elements which have the nature of donating electrons along with certain metallic properties are defined as metal. In the periodic table, these elements are located on the left side. Also, within the category, the metal property of elements along the period decreases, whole towards the down of the group, it generally increases because of increasing atomic radius in each element. Zinc, Iron, Gold, Copper, etc are some popular examples of metals.


Unlike metals, these elements possess an electron-accepting nature and are generally found on the right side of the Periodic Table or the atomic table of elements. This electron-accepting tendency is directly proportional to nuclear charge and inversely proportional to atomic size. Thus, for example, along the period, where the nuclear charge gradually rises, the tendency also increases. Whereas down the group, where atomic size increases, electron-accepting nature decreases.


These elements in the periodic table are referred to as the bridge between both metallic and non-metallic elements. Mainly because all the elements in the group have similar properties of certain metals as well as non-metals. Similar to the non-metals, these elements are located on the right side of the Periodic table.

Noble Gases

A unique set of 18 elements is located on the very right side of the periodic table, which is known for its filled electronic configuration. These elements include gases such as Helium, Radon, Krypton, etc.

Periodic Table Diagram

Periodic Table Diagram 

Periodicity of properties of elements

The properties of elements denote the periodic functions of their atomic number and this is this is the basic guiding rule. It must be noted that these properties reappear at regular intervals or follow a particular pattern at regular intervals. This phenomenon has been defined as the periodicity of elements.

How does periodicity define itself and how do periodic properties take place? Simple, the periodic properties of elements happen because of the recurrence of a similar electronic configuration that comes with the same number of electrons in the outermost orbit. If you consider a specific category, the number of valence electrons is always the same. But the valence electrons increase in their number when movement happens from the left to the right sides, across a period. The number of electrons in the valence shell establishes the chemical property of any element.

As explained above, the periodic properties of an element is determined by the valency and the number of shells present inside the atom. The shell number goes up as we move down a group. This is successive in such a way that the number of element shells is the same as the number of periods it is a part of. Now, if we travel across a period, this number remains unchanged.

Valency or the combined capacity of an atom equals the number of electrons an atom accepted or given to complete its octet. The outer shell of the atom determines the number of electrons present inside it. Now, come down in the group and the electron number, inside the valence shell remains constant. This infers the valency of a group is also constant. Valency always gives a positive value.

For any period, the number of electrons goes up as we go further right. This affects the electron’s number and eventually the octet.

Groups of Periodic Table

Currently, in the modern Periodic Table, there are 8 groups, such as 

  • Alkali Metals – All the elements in group 1 are regarded as Alkali Metals, mainly because they have a chemical reaction with water, which will result in alkali solutions. 
  • Alkaline Earth Metals – Similar to the group 1 elements, these elements change upon interacting with water from Alkaline solutions such as Hydroxides. 
  • Rare Earth Metals – Metals such as Lanthanum, Neodymium, Cerium, Scandium, etc. which exist in limited amounts in the earth’s crust are called Rare Earth Metals. 
  • Halogens – Upon reaction with the metals, these elements produce salts as end products. And elements such as Astatine, Chlorine, and Fluorine in Group 7A are called Halogens. 
  • Crystallogens – The elements of the carbon family are Lead, Carbon, Silicon, Germanium, etc. The Group 14 elements are referred to as Crystallogens. 
  • Chalcogens – Elements such as Oxygen, Polonium, Tellurium Sulphur, etc. That can be generally extracted from oxides and sulfide ores. 
  • Pnictogens – The elements of Group 15 are generally called the Nitrogen Family. The main characteristic of this family is their ability to produce suffocating and choking effects when oxygen is absent in the atmosphere. 

Elements of Periodic Table With Atomic Number

Elements   Symbol  Atomic Number 


Hydrogen  H  1 
Helium  He  2 
Lithium   Li   3 
Beryllium   Be  4 
Boron  B  5 
Carbon  C  6 
Nitrogen  N  7 
Oxygen  O  8 
Fluorine  F  9 
Neon  Ne  10 
Sodium  Na  11 
Magnesium  Mg  12 
Aluminum  Al  13 
Silicon  Si  14 
Phosphorus  P  15 
Sulfur  As  16 
Chlorine  Cl  17 
Argon  Ar  18 
Potassium  K  19 
Calcium  Ca  20 
Scandium  Sc  21 
Titanium  Ti  22 
Vanadium  V  23 
Chromium  Cr  24 
Manganese  Mn  25 
Iron  Fe  26 
Cobalt  Co  27 
Nickel  Ni  28 
Copper  Cu  29 
Zinc  Zn  30 
Gallium  Ga  31 
Germanium  Ge  32 
Arsenic  As  33 
Selenium  Se  34 
Bromine  Br  35 
Krypton  Kr  36 
Rubidium  Rb  37 
Strontium  Sr  38 
Yttrium  Y  39 
Zirconium  Zr  40 
Niobium  Nb  41 
Molybdenum  Mo  42 
Technetium  Tc  43 
Ruthenium  Ru  44 
Rhodium  Rh  45 
Palladium  Pd  46 
Silver  Ag  47 
Cadmium  Cd  48 
Indium  In  49 
Tin  Sn  50 
Antimony  Sb  51 
Tellurium  Te  52 
Iodine  I   53 
Xenon  Xe  54 
Cesium  Cs  55 
Barium  Ba  56 
Lanthanum  La  57 
Cerium  Ce  58 
Praseodymium  Pr  59 
Neodymium  Nd  60 
Promethium  Pm  61 
Samarium  Sm  62 
Europium  Eu  63 
Galdonium  Gd  64 
Terbium  Tb  65 
Dysprosium  Dy  66 
Holmium  Ho  67 
Erbium  Er  68 
Thulium  Tm  69 
Ytterbium  Yb  70 
Lutetium  Lu  71 
Hafnium  Hf  72 
Tantalum  Ta  73 
Tungsten  W  74 
Rhenium  Re  75 
Osmium  Os  76 
Iridium  Ir  77 
Platinum  Pt  78 
Gold  Au  79 
Mercury  Hg  80 
Thallium  Tl  81 
Lead  Pb  82 
Bismuth  Bi  83 
Polonium  Po  84 
Astatine  At  85 
Radon  Rn  86 
Francium  Fr  87 
Radium  Ra  88 
Actinium  Ac  89 
Thorium  Th  90 
Protactinium  Pa  91 
Uranium  U  92 
Neptunium  Np  93 
Plutonium  Pu  94 
Americium  Am  95 
Curium  Cm  96 
Berkelium  Bk  97 
Californium  Cf  98 
Einsteinium  Es  99 
Fermium  Fm  100 
Mendelevium  Md  101 
Nobelium  No  102 
Lawrencium  Lr  103 
Rutherfordium  Rf  104 
Dubnium  Db  105 
Seaborgium  Sg  106 
Bohrium  Bh  107 
Hassium  Hs  108 
Meitnerium  Mt  109 
Darmstadium  Ds  110 
Roentgenium  Rg  111 
Copernicium  Cn  112 
Nihonium  Nh  113 
Flerovium  Fl  114 
Moscovium  Mc  115 
Livermorium  Lv  116 
Tennessine  Ts  117 
Oganesson  Og  118 


The article above covered in great detail the Periodic Table, Classification of the Periodic Table, Groups of the Periodic Table, and Elements of the Periodic Table with Atomic Numbers. And there are many more complex topics such as these in the Chemistry subject, which students generally struggle to understand or learn. If that’s the case, then the Online Interactive Classes offered by Tutoroot might be a good choice for you.

Frequently Asked Questions

Which is the heaviest element in the periodic Table?

Oganesson was named after the Russian physicist Yuri Oganessian. This is presently the heaviest element in the atomic table of elements and weighs a humungous atomic mass of 300

What is the modern periodic table?

The present form of a periodic table or a modern periodic table is the table that is widely used across the globe consisting of the horizontal rows that are called periods and the vertical columns called.

How many elements are there in the periodic table

The periodic table has 118 elements

What is the Significance of Atomic Numbers?

The Atomic Numbers are essentially the number of protons present in each element, which makes them uniquely dissimilar to each other.

How many elements are there in the periodic table?

Currently, in the Modern Periodic Table, there are 118 elements.

How many groups are in the periodic table?

As stated above, the periodic table has 18 groups.

One thought on “What is a Periodic Table? – Definition, Elements, Groups

  1. I was recommended thіs ѡeb site by my сousin.
    I’m not sure whether this рost is written by him
    as nobody else know such detailеd about my difficulty.
    You are amazing! Thanks!

Leave a Reply

Your email address will not be published.