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.
(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 :
- 1
- 2
- 3
- 4
- 5
- 6
- 7
- 8
- 9
- 10
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