Mendeleev stated that ” The properties of the elements varies from member to member if the elements are placed in accordance with their increasing atomic-weight” and based on this law Mendeleev discovered the periodic table.
What is a periodic table?
A periodic table is the manifestation of periodic arrangements of elements in such a way so as to place chemically similar elements in the same vertical column.
The periodic table is divided into 7 periods which are as follows:
Period 1- Contains only two elements, Hydrogen (H) and helium (He).
Period 2- consists of 8 From Li to Ne.
Period 2 is the first short period that begins with an alkali metal Li and ends with an Inert gas Ne.
Period 3- period 3 also consist of eight elements Al, Mg, Na, Si, P, S, Cl and Ar.
This is the second short period.
Period 4- The 4th period begins with a strong electro positive alkali metal K and ends with an inert gas Kr. This period contains 18 elements and is known as the first long period.
The 4th period is subdivided into a subgroup A and a subgroup B.
The sub group A contains the elements from K to Ge and the subgroup B contains the elements such as Cu, Zn, Si, Ti, etc.
The 4th period also contains the transition elements.
Period 5- This period contains 18 elements from Rb to Xe. This period contains both typical and transition elements and is referred to as the 2nd long period of the periodic table.
Period 6- this period contains 32 elements and is known as a very long period.
This period contains the typical elements from Cs to Rn and 10 transition elements from La to Hg. This period further contains 14 rare elements or lanthanides. These elements are present in nature to a negligible extent and thus these 14 elements are also called as rare earth elements.
Period 7- Contains 19 elements and is known as the incomplete period.
Filed under: Periodic Table With Charges
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