• 1.According to Bohr atom model the electrons are revolved around the nucleus in a fixed
    circular path is called orbit.
  • 2.The maximum electron embedded in 1st shell(K) =2                                                                
  • 3.The maximum electron embedded in 2nd shell (L)=8                                                                     
  • 4. The Maximum electron at 3rd shell(M) = 18 
  • 5.Accordingly electron in each energy level  are arranged in its sub energy level 
    6.Each sub energy level in a shell is called a sub shell,They are named as s p d & f
  • 7.Electron filling in different sub shells takes place in the increasing order of their
    energies.ie the sub shell which has the lowest energy level is filled first.
  • 8. The increasing order of sub shell can be identify from the following diagram.
  • 9.Based on the sub shell electronic configuration, elements are classified into four
    different blocks as s p d & f.         
  • 10.The block to which the element belongs will be the same as the sub shell to which
    the last electron is added. 
  • 11.the period number is same as the shell number of the outermost shell in the sub shell
    electronic configuration
  • 12.for s block elements the number of electron in the outer most s sub shell
    will be the group number
  • 13.Pblock: Group number is obtained by adding 12 to the number of electron present in the outermost p sub shell
  • 14.Dblock:the group number of d block elements will be the same as the sum of electrons in the outermost s sub shell and the number of electron in the preceding d sub shell

Characteristics of s block elements:

  • 15.Their oxide and hydroxides are basic in nature.
  • 16.S block elements usually form ionic compounds
  • 17.More metallic nature
  • 18.Low ionization energy
  • 19.Low electro negativity
  • 20.Elements in 1st & 2nd group are belong to s block elements.( 1st group element is alkali
  • metals and 2nd group elements is alkaline earth metals)
  • 21.Oxidation state of 1st group element is +1 &oxidation state of 2nd group elements is +2
  • 22.High atomic radius.Last electrons are filled in s sub shell

Characteristics of p block elements: 

  • 23.P block contains metals, non metals and metalloids.
  • 24.The last electron is filled in p sub shell 25.High ionization energy
  • 26.High electro negativity
  • 27.P block elements shows both +ve and –ve oxidation state.

Characteristics of d block elements: 

  • 28.The last electron is filled in the d sub shell
  • 29. Their elements are also known as transition elements.
  • 30.All d block elements are metals.

Characteristics of f block elements:

  • 31 the element in which last electron enter into the f sub shell
    their elements are also known as inner transition elements.
    Their elements are placed in two separate rows at the bottom of the
    periodic table.
  • 32 1st row known as lanthanoids     
  • 33.2nd row known as actinoids 
  • 34.Most of the elements shows variable oxidation state liked block elements
    Most of the actinoids are artificial elements.
    Uranium(U), thorium (Th), plutonium (Pu) etc… are used as fuel in
    nuclear reactor.
  • 35.Many of these elements are used as catalyst in the petroleum industry.

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