9th Class Chapter 2 Chemistry Long Questions

Describe Rutherford's atomic model. Also state the observation made by Rutherford.

Rutherford's Atomic Model Rutherford performed gold Foil ' experiments to understand how negative and positive charges could coexist in an atom. He bombarded alpha particles on a 0.00004cm thick gold foil. Alpha particles are emitted by radioactive elements like radium and polonium These are actually helium nuclei (He²+) they can penetrate through matter to some extent He observed the effects of x-particle on a photographic plate or a screen coated with zinc sulphide He proved that the "Plum pudding" model of the atom was not correct. Scattering of x particles Observations: Observations made by Rutherford were as follows Almost all the particles passed through the foil undeflected. Out of 20000 particles, only a few deflected at fairly large angles and very few bounced back on hitting the gold foil.

Write the properties of canal rays.

Properties of Canal Rays: The properties of these rays were as following: These rays travel in straight lines in a direction opposite to the cathode rays. Their deflection in electric and magnetic field proved that these are positively charged. The nature of canal rays depends upon the nature of the gas, present in the discharge tube. These rays do not originate from the anode. In fact, these rays are produced when the cathode rays or electrons collide with the residual gas molecules present in the discharge tube and ionize them as follows: M +e^- __________> M ^+ 2e^- Mass of these particles was found equal to that of a proton or simple multiple of it. The mas of a proton is 1840 time more than that of an electron.

Write a note on shell and subshell.

Shell: Shells are the main energy levels that electrons can occupy shells are represented by circles around the nucleus. They are counted from the center to outward. The number of electrons that a shell can accommodate is given by 2n², where n is the shell number. Energy levels are represented by n values 1,2,3 and so on . They are designated by the alphabets k, L, M and so on. A shell closer to th nucleus is of minimum energy . Since k shell is closest to the nucleus, They energy of shells increases from k shell onwards Subshell: A shell also consists of subshells the number of subshells in a shell is equal to its n value. Each subshell is designated by a small alphabetical letters s, p,d,f etc n value Shell Subshell 1 k s,p 2 L s,p,d 3 M s,p,d 4 N s,p,d,f

Write five characteristics of cathode rays

Characteristics of Cathode Rays: The characteristics of cathode rays were determined, which are given below: 1- These rays travel in straight lines perpendicular to the cathode surface. 2- They can cast a sharp shadow of an opaque object if placed in their path. 3- They can deflect towards the positive plate in an electric field showing that they are negatively charged. 4- Light is produced when these rays hit the walls of the discharge tube 5- It was found that the same type of rays were emitted no matter which gas and which gas and which cathode was used in the discharge tube

State the postulate of Bohr's atomic model?

The Boht's atomic model was based upon the following postulates:

Write a detail note on cathode rays and discovery of electron?

Introduction: in 1879 Sir William rooks performed experiment by passing electric current through gas in a discharge tube at very low pressure.

Write the detail note on discovery of proton?

Introduction: in 1886 Goldstein observed that IN addition to cathode rays, other rays were also present in the discharge tube. These rays were travelling in opposite to direction of cathode rays.

Explain discovery of neutron

Introduction: Rutherford observed that atomic mass of the element could not be explained on the basis of the masses of electron and proton only. He predicted in 1920 that some neutral particles having mass equal to that of proton must be present in an tom. Thus scientists were in search of such a neutral particle.

Explain Rutherford atomic model

Introduction: In 1911, Lord Rutherford proposed an atomic mode, in which he state different properties about an atom. Rutherford preformed " Gold foil" experiment to understand how negative and positive charges could co-exist in an atom

Describe the postulates of Bohr's atomic model<div>Or</div><div>How did Bohr proved that atom exists?</div>

Introduction: In 1913 , Neil Bohr presented another model of atom. The quantum theory of Max Planck was used as foundation for this model.

What us meant by electronic configuration? briefly explain s and p subshells<div><br></div>

Electronic configuration:" the particular arrangement of electrons in the shells and subshells is called electronic configuration".

What us meant by electronic configuration? briefly explain s and p subshells<div><br></div>

Electronic configuration:" the particular arrangement of electrons in the shells and subshells is called electronic configuration".

Briefly describe the filling sequence of electrons in shells and sub-shells?

The distribution of electrons around the nucleus in various shells and sub-shells has been occurred according to their increasing energy.

Define and explain isotopes. Discuss the structure of isotopes with suitable examples

Isotopes:

Give important uses of isotopes

Isotopes: isotopes are defined as the atoms of an element that have same atomic number but different mass number.