Class 11 Chemistry Structure of Atom | Quantum Mechanics |

__QUANTUM MECHANICS __

It was given by Schrodinger. He said if we take both the characters in account that is particle character and wave character, we have to define a property that is a wave function.

__Schrodinger wave equation__

On the basis of it Schrodinger simplified equation as:

**Physical significance of wavefunction:** **”**

- It gives the amplitude associated with it. But if we do square of it, than it gives the probability of finding the electron in particular region.

**Orbital**: It is three-dimensional space, where probability of finding an electron in maximum.

**Difference between orbit and orbital:**

**Orbital: They are of four types **

- s orbital: Spherical in shape, non-directional. It has only 1 orbital therefore, can accommodate only 2 electrons.
- P-orbital: dumb-bell shaped and directional. It has 3 orbital (p
_{x}, p_{y}, p_{z}). It can accommodate maximum of 6 electrons. - d-orbital: It has double dumbbell, directional. It has 5 orbital (d
_{xy},d_{yz},d_{zx},d_{x2-y2},d_{z2}).It can accommodate maximum of 10 electrons - F-orbital: It has diffused shape. It has 7 orbital therefore, can accommodate maximum of 14 electrons.

** **

**Quantum numbers**

They are set of 4 numbers, which give complete information about the address of electron.

**There are 4 types of quantum numbers:**

- Principal quantum number.
- Azimuthal quantum number.
- Magnetic quantum number.
- Spin quantum number.

**Principal quantum number**:

- It is represented as ‘n’.
- It was given by Bohr.
- It represents the orbit where electron is going to be present.

Uses:

- It gives number of electron in orbit by formula 2 n
^{2}. - It gives angular momentum of electron.
- It gives energy of electron.
- It gives radius of orbit.

**Azimuthal quantum number:**

- It gives information about sub shell of an atom.
- It is represented as ‘l’.
- It was introduced by Somerfield.
- It always has value (n-1).

Example: if n=1 ,l=0

If n=2,l=0,1

If n=3,l=0,1,2

**Magnetic quantum number**:

- It describes the behavior of electron in magnetic field.
- It is represented as ‘m’.
- It was given by land.
- Its value is equal to –l,0, +l

For example: if n=1, l=0, m=0 that is only one orbital

If n=2, l=0,1, m=-1,0, +1 that is three orbitals

**Spin quantum number:**- It gives the info about spinning of electron about its axis i.e. clockwise or anticlockwise
- It is denoted by ‘s’.
- Its value is either =+1/2, -1/2

**Problem**: Write down the quantum numbers n , l and m for the

Following orbitals:

- 3d
_{x}^{2 }–_{y}^{2 } - 4d
_{z}^{2 }

Answer :-

n=3, l=2, m=+2

N = 4, l=2, m=0

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