Periodic Table

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The periodic table is the tabular arrangement of elements, according to their atomic number, to study the periodic behavior of their physical and chemical properties. It is a symbol of chemistry but is widely used in physics and all other sciences. It tells us that when elements are arranged in order of increasing atomic number, their properties are repeated. In this article, we will discuss the history, structure, and trends of the periodic table.

History

The history of the periodic table is as follows:

NAME OF SCIENTIST	YEAR	CONTRIBUTION
AL-RAZI	9^th Centaury	Divided all substances into four categories: · Vegetable · Animal · Derivative · Mineral His classification is based on the physical and chemical properties of substances.
DOBEREINER	1829	Arranged elements known at that time into Triads.
JOHN NEWLANDS	1863-64	Arranged elements in increasing order of atomic weights. Proposed Law of Octaves
LOTHAR MEYER	1864	Plotted atomic masses vertically and atomic volumes horizontally to arrange elements.
DMITRI MENDELEEV	1871	Presented FIRST REGULAR PERIODIC TABLE
ANTONIUS VAN DEN BROEK	1911	Gave hypothesis of atomic number.
HENRY MOSELEY	1911	Discovered atomic number experimentally by using X-ray spectroscopy.

After the discovery of atomic number, the periodic table was rearranged and atomic mass was replaced with atomic number which was a major improvement in Mendeelev’s periodic table and it leads us to the Modern periodic table.

MODERN PERIODIC TABLE

The essential features of the periodic table are given below.

Groups and periods
Families
Blocks
Metals, Non-metals and Metalloids

GROUPS AND PERIODS

The periodic table is divided into vertical columns called groups and horizontal rows called periods.

Differentiation between the two of them is given below:

GROUPS	PERIODS
Vertical columns in the periodic table	Horizontal rows in the periodic table
8 groups in the periodic table.	7 rows in the periodic table.
Each group is divided into two subgroups i.e A and B	Periods are numbered in Arabic numerals i.e 1 to 7
Elements in A subgroups =Normal elements( IA to VIA) Elements in B subgroups =Transition elements( IB to VIIIB)	Elements in periods are arranged as follows: · Period 1=shortest period=2 elements · Period 2 ,3=short periods=8 elements each · Period 4,5=long periods=18 elements each · Period 6,7=very long periods=32 elements in 6^th one Ø 7^th period is incomplete yet contains 32 elements.
Elements in one group possess similar properties.	Elements in one period possess entirely different properties.
Groups are numbered in Roman numerals.	6th period consists of Lanthanides.
	7th period consists of Actinides.

FAMILIES IN THE PERIODIC TABLE

Following are the families of the periodic table.

FAMILY NAME	GROUP NO. or ELEMENTS
ALKALI METAL	GROUP IA
ALKALINE EARTH METAL	GROUP IIA
TRANSITION METALS	GROUP IB to VIIIB
NON METALS	Upper elements of GROUP IVA TO VIA
HALOGENS	GROUP VIIA
NOBLE GASES	GROUP VIIIA
METALLOIDS	SOME ELEMENTS OF GROUP IIIA to VIA

BLOCKS

The periodic table comprises of four blocks.

s block	Group IA and IIA elements
p block	Elements of group IA to VIIIA Except Helium
d block	Transition Elements
f block	Inner transition elements

METALS, METALS AND METALLOIDS

A list of metals, nonmetals, and metalloids is given below:

SUBSTANCE	ELEMENTS
METALS	All other elements except non-metals and metalloids
NONMETALS	H, He, C, N, P, O, S, Se, F, Cl, Br, I and noble gases(17 elements)
METALLOIDS	B, Si, Ge, As, Sb, Te, Po (7 elements)

TRENDS IN THE PERIODIC TABLE

Chemical properties of elements tend to vary steadily along the group or period. Hence

some common trends of physical properties varying in the periodic table are given below:

PHYSICAL PROPERTY	GROUPS( TOP TO BOTTOM)	PERIODS(LEFT TO RIGHT)
ATOMIC SIZE	INCREASE	DECREASE
IONIZATION ENERGY	DECREASE	INCREASE
ELECTRON AFFINITY	DECREASE	INCREASE
ELECTRONEGATIVITY	DECREASE	INCREASE
METALLIC CHARACTER	INCREASE	DECREASE

Periodic Table

History