Long Form of Periodic Table
Till today more than 112 elements have been discovered. These elements have diverse existence and properties. Many scientists have contributed to the earlier classification of elements.
The first successful classification of elements was given by a Russian chemist, Dmitri Mendeleev.
Mendeleev used atomic weight as the basis of classification of elements in the periodic table which consists of 8 vertical columns (groups) and 7 horizontal rows (periods).
9th vertical column called zero group was also added with the discovery of inert gases.
There were some drawbacks in Mendeleev's periodic table.
To overcome these drawbacks, Henry Moseley gave a modern periodic table based on his modern periodic law.
Moseley found that the properties of the elements varied periodically with atomic number.
Atomic number, as the important characteristic of an atom led to the modern periodic law.
Modern periodic table is based on modern periodic law.
Many versions of this periodic table are in use but the most commonly used is the long form of modern periodic table.
Periodicity is an important term to know about the long form of periodic table.
The long form of periodic table is given by Bohr & Bury.
Long form of periodic table comprises of 7 horizontal rows (periods) & 18 vertical columns (groups).
First period contains 2 elements. The subsequent periods consists of 8, 8, 18, 18 and 32 elements respectively.
6th and 7th period have 32 elements in each, of which, 14 elements series called Lanthanide series and Actinide series, are placed separately below the main body of periodic table.
Elements of the same group have similar valence shell electronic configuration.
The number of a period indicates the value of principal shell (n).
To name the elements having atomic number more than 100, the numerical roots are put together in order of digits as they appear in atomic number and ium is added at the end.
Based on the name of the orbital that receives the last electron, elements are classified into four blocks, s block, p block, d block and f block.
The s and p block elements are collectively called representative elements.
Group 1 elements are known as alkali metals, group 2 as alkaline earth metals, group 16 elements as chalcogens, group 17 elements as halogens and d block elements as transition elements.
The modern periodic table has 8 families namely lithium family, beryllium family, boron family, carbon family, nitrogen family, oxygen family, halogen family and noble gases.
The elements in any group of the periodic table have similar physical and chemical properties.
On the basis of properties, elements can be classified into metals, non-metals and metalloids (semi metals). The long form of periodic table has many advantages.
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