Q2 of 64 Page 110

An atom with atomic number 9 and mass number 19 will have the following constituents:

We know that,


Atomic number = Number of protons = 9.


Hence, 9p


Mass number = Number of protons + Number of neutrons


⇒ 19 = 9 + Number of neutrons


⇒ Number of neutrons = 19-9 =10


Hence, 10n


Now, Number of electrons = Number of protons


⇒ Number of electrons =9


Hence, 9e


Therefore the correct option is B

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On the basis of Rutherford’s model of an atom, which subatomic particle is present in the nucleus of an atom?

 1

The number of valence electrons in CL ion are:

 3

An alpha particle is also known as:

 4

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

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


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


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


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