Atomic structure

bohr's atomic model-

postulates-

1.electrons revolve around nucleus in concentric circular path called orbit situated at definite distance from the nucleus.

2.as long as electron remains in particular orbit, it neither emits nor absorbs energy.

3.different stationary levels are represented as K,L,M,N.

4.Energy go on increasing as we go away from nucleus.

5.a definite amount of energy is absorbed when electron jump from lower energy level to higher energy level and electron jumps from higher energy level to lower energy level and releases energy which is equal to difference between  that 2 energy levels . 

6. an electron can move in that stationary orbit without radiating energy for which angular momentum(mvr) is equal to integral multiple of h/2pi                      

  for K shell    n=1 , for L shell  n=2, for M shell   n=3 , for  N shell  n=4.    

   

                                                                                                        

Idea of shell , sub shell and orbital-

1. shell-

the orbit in which electron revolves is called as principal energy level or shell. the maximum no. electrons that revolves in particular orbit is equal to 2n^2.

2. sub shells-

a principal shell is further divided into sub shell.     

       

                 

   3. orbital-

the 3-d region around nucleus in which probablity of finding electron is more is called orbital.

each sub shell is further divided into one or more energy  states called as orbitals.                 

                           

 shapes of s and p orbitals-

s orbital-

s orbital is non directional.

it is spherically symmetrical around the nucleus.

the size and energy of s orbital increases with increase in principal energy level that is in order 4s>3s>2s>1s.

p orbital-

p orbital is dumb bell shaped ,having 2 lobes on either sides of the imaginary plane that passes through nucleus.

there are 3 orientations of the electron cloud in p orbital,along the 3 co-ordinate axes x,y and z.

the size and energy goes on increasing in order 4p>3p>2p>1p.

the size,shape and energy of 3 orbitals are identical.

Quantum numbers-

the numbers which are used to identify the various energy states of an electron is called quantum numbers.

following 4 are quantum numbers

1. principal quantum number(n)-

indicates the main or principal energy level of electron

determines the size of the electron cloud

it also gives information about maximum no of electrons can be acoomodated in a shell.

2. azimuthal / subsidiary / orbital quantum number (l)-

gives shape of orbital

gives subshell to which electron belogs

magnetic quantum number(m)-

indicates the spatial orientation of each sub shell i external magnetic field

positive value of m indicates orientation of orbital and magnetic field are in same direction. negative value of m indicates orientation of orbital and magnetic field are in opposite direction.

spin quantum number(s)-

it gives information about revolution of electron about its own axis.

+1/2 for clockwise and -1/2 for anticlockwise.

order of filling of atomic orbitals

anomalous behavior of Cu and Cr-

it is for attaining more stability in Cu and Cr by having completely filled or half filled orbitals.