CBSE Important Questions

CBSE Guess > Papers > Important Questions > Class IX > 2009 > Science > Science By : Mr M. p. Keshri

CBSE CLASS I X

Structure Of The Atoms (Solved)

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Q.117. The distribution of electrons, neutrons and protons are given below:

Elements Electrons Neutrons Protons
A 4 4 3
B 8 9 9
C 18 22 18
D 17 20 17
E 17 18 17

         
From the above data find –

(i) a cation,

(ii) an anion,

(iii) atom of noble gas.


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Q. 118. What is meant by atomic number of an element ? What happens to the atomic number of an element when its atoms form ions ? Give example each of diatomic and triatomic molecules.


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Q. 119.Find the atomic number of an element which has 7 electrons in the M shell.


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Q. 120. The atomic number of chlorine is 17. Write the number of electrons in Cl-.   


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Q. 121. There are 2 electrons in M shell of an element. Find the atomic number of the element.


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Q.122. Is there any change of atomic number when an element forms ions ?


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Q. 123. The atomic number of aluminium and chlorine are 13 and 17 respectively. Find the number of electrons present in Al+3 and Cl- respectively.


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Q. 124. Why certain atoms are radioactive while many others are not ?


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Q. 125. State the electronic configuration attained by chemically inert substances.


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Q. 126. 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 ?

(ii) what is the charge on the atom ?


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Q. 127. Define isotope with suitable example.


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Q. 128. Two atoms A & B of chlorine have same nuclear charge. Mass number of A is 35 and mass number of B is 37. What are the atoms collectively called ? What is the difference between two ? Do they have same chemical properties ?


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Q. 129. Write the similar properties of isotopes.


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Q. 130. State the uses of isotopes.


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Q. 131. Atomic mass of an element is equal to the sum of number of protons and neutrons and is a whole number. How the fractional atomic masses of element is accounted ?


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Q. 132. Two atomic species A & B have the composition of their nuclei. Number of protons in both A & B are 6 while number of neutrons in A is 6 & in B is 8. State the relation between A & B and guess the elements which they represent.


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Q.133. Two atomic species X & Y have the composition of their nuclei. Number of protons in both X & Y are 8 while number of neutron in X is 8 and in Y is 10. State the relation between X & Y and guess the element they represent.


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Q. 134. A & B are two atoms whose nuclei contains protons and neutrons as under :

Atoms

A

B

Number of protons

6

6

Number of neutrons

6

7

                             
State the relationship between A & B and find the element they represent.


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Q.135. “Isotopes of an element differ in atomic masses and not in atomic number.” Comment.       

           
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Q. 136. The number of electrons, protons and neutrons of species A, B, C, D, E are as under :

Species

Electrons

Protons

Neutrons

A

4

6

6

B

18

18

22

C

17

17

20

D

11

9

10

E

17

17

18

Find from the table given above the species that represent :

(i) A cation

(ii) An anion

(iii) An atom of inert gas

(iv) A pair of isotopes.


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Q.137. The relative atomic mass of an element X is 16.2. Calculate the percentage of 16X8 and 18X8 isotopes in a sample of X. 


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Q. 138.  X, Y and Z are elements whose nuclei contains protons and neutrons as under :

Atoms

Protons

Neutrons

X

1

0

Y

1

1

Z

1

2

                           
Name the elements and find their relations.


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Q. 139. Why isotopes of elements have the same chemical properties but different physical properties ?


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Q. 140. Define half-life.

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