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A certain nucleus X has a mass number 15 and atomic number 7.

(a)  Find the number of neutrons.

(b)  Write the symbol for the nucleus X.

(c)  The nucleus X loses (i)  one proton, (ii)  one -particle, (iii) one - particle. 

Write the symbol of the new nucleus in each case and express each change by a reaction.

Asked by Topperlearning User 4th June 2014, 1:23 PM
Answered by Expert

(a)  Mass number = number of protons + number of neutrons and atomic number = number of protons.

Therefore, number of neutrons = mass number - atomic number = 15 - 7 = 8.

(b)  Element X can be written as .

(c) (i) After the loss of 1 proton, the mass number and atomic number of the nucleus will decrease by 1.  The new nucleus will be (say).  The change can be written as :

(ii) After the loss of one -particle, the mass number will remain the same but the atomic number will increase by 1.  The element changes to (say) as follows :

(iii)  After the loss of one -particle, the mass number decreases by 4 and the atomic number decreases by 2.  The element changes to (say) as follows :

Answered by Expert 4th June 2014, 3:23 PM
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