Available Answers

1. 1.

   The modern atomic theory correlates and contradicts with - Dalton's atomic theory. Give reasons for the same.

2. 2.

   

   The above diagrams represents the experiments conducted by

   1. J.J. Thompson which led to the discovery of electrons
   2. Goldstein's experiment which led to the discovery of protons
   3. Rutherford's experiment which led to the discovery of the atomic nucleus.

   Match the statements in - Column I pertaining to the discovery of the structure of an atom with the relevant continuity statement in - Column II.

   COLUMN I	COLUMN II
   A. J.J. Thompson studied the characteristics of cathode rays and found that	1. unit positive charge and a mass equal to 1837 times the mass of an electron [i.e. mass equal to 1 atomic mass unit].
   B. Electrons are also emitted by	2. most of the matter in an atom is located in a very little space called 'nucleus' and electrons revolve around the nucleus to confer stability of the atom.
   C. The charge and mass of an electron is	3. neutral i.e.. carry no electric charge and have a mass almost equal to the mass of a proton [i.e. mass equal to 1 atomic mass unit].
   D. Goldstein discovered rays emitted from the anode	4. nucleons
   E. The charge and mass of a proton is	5. in the nucleus of an atom are present particles which possesses no charge but have a mass equal to that of protons.
   F. Lord Rutherford studied the atomic model and through his experiments of projection of alpha particles on thin metallic sheets discovered	6. they contain negatively charged particles now called 'electrons'.
   G. The conclusion drawn from Rutherford's atomic model were that	7. unit negative charge and a mass 1/1837 of the mass of a hydrogen atom or proton [i.e. negligible mass]
   H. James Chadwick discovered the neutron and concluded that	8. action of heat or U.V. light on certain metals.
   I. The charge and mass of a neutron is	9. consisting of positively charged particles called 'protons'.
   J. Protons and neutrons are together known as	10. the atomic nucleus.

3. 3.

   The diagram below represents an atom. Complete the labelling of the atom given below indicating the subatomic particles, nucleus and orbits.

   

4. 4.

   The symbols given below represent the subatomic particles i.e., protons, electrons and neutrons. Complete the blanks for the subscript and superscript numbers of 'e' and 'n'.

   

5. 5.

   Complete the statements given below :

   1. The protons and neutrons are present in the _____________ of an atom.
   2. The subscript number of 'p' represents the charge/mass.
   3. The mass of a proton is equal to _____________ a.m.u. [atomic mass units]
   4. Protons carry unit positive/negative charge, while electrons carry unit positive/negative charge.
   5. The mass of an electron is considered as 1 a.m.u/negligible.
   6. The superscript on 'n' represents its charge/mass.
   7. The electrons revolve around the nucleus in imaginary paths called _____________.
6. 6.

   Complete the statements given below by selecting the correct statement/word - in each of the following representations of an atom.

   1. Atomic number
      1. Elements are arranged in serial order on the basis of the number of : protons/neutrons/electrons in their respective atoms.

   This number is called atomic/mass number of the element and is denoted by 'Z'.

   2. Atomic number of an element is the number of :
      1. protons/neutrons in the nucleus of an atom
      2. electrons/neutrons in the complete atom
      3. positive/negative charges in the nucleus of its atom.
   3. Atomic number [Z] is equal to:
      1. Z=p=e;
      2. Z=n=e;
      3. Z=pen.

   2. Mass number of an atom is :

   1. The total number of neutrons/protons and electrons in the atom.
   2. The mass number is slightly less/more than the actual atomic mass.
   3. Mass number [A] is equal to :
      1. A=p + e;
      2. A=n + p;
      3. A=n - e.