PROPERTIES OF CATHODE RAYS.

The nature of cathode rays was extensively investigated by J.Hittorf (1869);William Crookes (1870);J.Perrin (1895)and J.J.Thomson (1897).

👉Some of the improtant properties are mentioned here-

1) The properties of the cathode rays are independent of the nature of the gas present in the discharge tube or the nature of cathode.

2)They travel in straight lines perpendicular to the surface of the cathode.

 

3) They possess momentum and kinetic energy by virtue of which they can cause a mechanical motion in small paddle wheels placed in their path of traveling.

4)  They can produce ionisation in gases.

 

5) They can effect the photographic plates.

6) These are deflected by eletric and magnetic fields. The mode of deflection indicates that they consist of minute particles carrying negative charge. These particles are named electrons.

7) They can produce fluorescence when incident on the glass walls of the discharge tube.Zinc sulphide also becomes fluorescent when placed in the path of the cathode rays.

Explain why 2d and 3f orbitals do not exist.

⇛The value of azimuthal quantum number l decides which type of orbitals(s,p,d or f) would be included in a particular shell. In the case of d and f the values of l are 2 and 3 respectively. Now for n=2,the only possible values of l are 0 and 1. So for the second shell (n=2) d sub-shell cannot exist i.e. there is no existence of d orbital. Similarly when n=3, l will have the values of 0,1,2. Naturally there is no existence of f sub-shell in the Shell number 3; i.e. 3f and 2d orbital will be non-existent...

What is the difference between the notations L and l.

⇛L represents second Bohr orbit for which n=2. On the other hand l denotes azimuthal quantum number which may have values 0,1,2 etc. Shapes of various sub-shells present within the same principle shell number of sub-shells in a certain shell and their relative energies etc.depend on the values of 'l'.

For example,in case of s,p,d & f sub-shells, the value of l are 0,1,2 & 3 respectively. 

Discuss the limitation of Bohr's theory on the basis of Heisenberg's uncertainty principle.

  ⇛According to Bhor's theory negatively charged particles(electrons) inside an atom revolve around the nucleus in well defined orbits having fixed radius. In order to balance the nuclear attractive force electron must move with a definite velocity. But according to uncertainty principle it is impossible to determine simultaneously the exact position and momentum of a microscopic particle like electron. Thus Bohr's model contradicts Heisenberg's uncertainty principle...

Mention differences between wave and particle.

1)Wave is delocalised in space.

Particle is localised in space.

2)Two or more waves can exist simultaneously in the same region in space.

More than one Particle cannot occupy the same position in space at the same time.

3)When two waves are present together in the same region they may undergo constructive or destructive interference.

Particles do not show the phenomenon of interference.. 

Is there any significance of uncertainty principle in our daily life?

In our daily life we deal with objects of ordinary size. So the uncertainties in their position and momentum are very small as compared to the size and momentum of the object respectively. So such uncertainties may be neglected. Thus uncertainty principle has no significance in our daily life...

Why does polarity develop in a bond?

⇛when two atoms having different electronegativities i.e.,attraction for electrons, are joined by a covalent bond,the shared pair of electrons forming the bond is attracted more towards the more electronegative atom of the two.As a result of this unequal distribution of the bonding electrons one end of the bond becomes relatively negative and the other positive i.e. a polarity developes within a bond.

An example of such a polar covalent bond is the one in HCl. The Cl atom with its greater electronegativity pulls the bonding electrons towards itself. As a consequence the Cl atom becomes partially negative and the H atom becomes partially positive. So the molecule is a dipolar...