Science - Class 9

Q46. In the Thomson’s model of atom, which of the following statements are correct?

(i) The mass of the atom is assumed to be uniformly distributed over the atom.

(ii) The positive charge is assumed to be uniformly distributed over the atom.

(iii) The electrons are uniformly distributed in the positively charged sphere.

(iv) The electrons attract each other to stabilise the atom.

(a) (i), (ii) and (iii)

(b) (i) and (iii)

(c) (i) and (iv)

(d) (i), (iii) and (iv)

 

Q47. If K and L shells of an atom are full, then what would be the total number of electrons in the atom?

 

Q48. Write the electronic configuration of any one pair of isotopes and isobars.

 

Q49. If number of electrons in an atom is 8 and number of protons is also

8, then (i) what is the atomic number of the atom? and (ii) what is the charge on the atom?

 

Q50. Helium atom has an atomic mass of 4 u and two protons in its nucleus. How many neutrons does it have?

 

Q51. The number of electrons in an element X is 15 and the number of neutrons is 16. Which of the following is the correct representation of the element?

 

Q52. What information do you get from the figure about the atomic number, mass number and valency of atoms X, Y and Z? Give your answer in a tabular form.

 

Q53. Which of the following in Fig. do not represent Bohr’s model of an atom correctly?

(a) (i) and (ii)

(b) (ii) and (iii)

(c) (ii) and (iv)

(d) (i) and (iv)

 

Q54. Rutherford’s α-particle scattering experiment showed that

(i) Electrons have negative charge.

(ii) The mass and positive charge of the atom is concentrated in the nucleus.

(iii) Neutron exists in the nucleus.

(iv) Most of the space in atom is empty.

Which of the above statements are correct?

(a) (i) and (iii)

(b) (ii) and (iv)

(c) (i) and (iv)

(d) (iii) and (iv)

 

Q55. Find out the mass number of oxygen and sulphur atom.

 

Q56. What are the limitations of Rutherford’s model of the atom?

Or

What were the drawbacks of Rutherford’s model of an atom?

 

Q57. Define valency by taking examples of silicon and oxygen.

 

Q58. Write any two observations which support the fact that atoms are divisible.

 

Q59. Complete the following table.

Atomic Number	Mass Number	Number  of Neutrons	Number  of Protons	Number  of Electrons	Name of Atomic Species
9	-	10	-	-	-
16	32	-	-	-	Sulphur
-	24	-	12	-	-
-	2	-	1	-	-
-	1	0	1	0	-