STRUCTURE OF ATOM, Class 9

STRUCTURE OF ATOM

1. Name the three subatomic particles of an atom.
   Ans : (i )Electrons (negatively charged)
   (ii) Protons(positively charged)
   (iii) Neutrons(no charge)
   
2. What are canal rays ?
   Ans : Canal rays are positively charged radiations which led to the discovery of positively charged sub- atomic particle called proton.


3. If an atom contains one electron and one proton, will it carry any charge or not?
   Ans : The atom will be electrically neutral as one negative charge balances one positive charge.


4. On the basis of Thomson's model of an atom, explain how the atom is neutral as a whole.
   Ans: According to Thomson's model of an atom-
   (i) An atom consists of a positively charged sphere and the electrons are embedded in it.
   (ii) The negative and positive charges are equal in magnitude. So, the atom is electrically neutral.


5. On the basis of Rutherford's model of an atom, which sub-atomic particle is present in the neucleus of an atom ?
   Ans :- Proton is present in the neucleus.


6. Draw a sketch of Bohr's model of an atom with three shells
   Ans :-
   









7. What do you think would be the observation if the α - particle scattering experiment is carried out using a foil of a metal other than gold?
   Ans :- On using any metal foil, the observations of the α - particle scattering experiment would remain the same as all atoms would hav same structure.


8. What do you mean by atomic number?
   Ans :- Atomic Number (Z) :- The total number of protons present in a nucleus of an atom is called its atomic number.


9. What do you mean by atomic number?
   Ans :- Mass number (A) :- The sum of total number of protons and neutrons present in the nucleus of an atom is called its mass number.


10. How the atomic number(Z), mass number (A) and symbol of an element are represented?
    Ans :-
11. Write the name and symbols of the elements from the atomic number 1 to 10. Also write the number of protons and electrons also.


12. Write the name and symbols of the elements from the atomic number 11 to 20. Also write the number of protons and electrons.


13. Write the name and symbols of the elements from the atomic number 21 to 30. Also write the number of protons and electrons .


14. Write the name and symbols of the elements from the atomic number 31 to 40. Also write the number of protons and electrons .


15. What do you mean by isotopes?
    Ans :- Isotopes: The atoms of same element having same atomic number but different mass numbers are called isotopes of that element.


16. What are the isotopes of hydrogen?
    Ans: There are three isotopes of hydrogen.
    (i) Protium (ii) Deuterium (iii) Tritium


17. Show the number of electrons, protons and neutrons of isotopes of hydrogen.



18. What subatomic particles are different in number in isotopes of the same element?
    Ans: neutrons


19. What do you mean by isobars?
    Ans:- Isobars : The atoms of different elements having same mass number but different atomic numbers are called isobars.


20. Give example of isobars.
    Ans :


21. Write the symbols of elements from atomic number 1 to 20 with the representation of atomic number and mass numbers.


22. Write the number of protons , electrons and neutrons of Al and Mg.
23. Write the number of neutrons of O and N.
24. Atomic number of an element is p and its number of neutrons is q and its symbol is A. How to represent this element symbolically?