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 forms 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?

Let us first begin with an understanding of the periodic table. Before we get into the topic, let us understand the History of the Periodic Table. In 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 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, which 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 

Metals

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.

Non-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.

Metalloids

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

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

Conclusion

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.

For more simplified explanations like the one above, visit the chemistry blogs on the Tutoroot website. Elevate your learning with Tutoroot’s personalised Chemistry online tuition. Begin your journey with a FREE DEMO session and discover the advantages of online tuition classes.

FAQ’s

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.