Question

plzz Ans 15 question just represent in terms of mass and atomic number no need to give elements name

Answer 1

phosphurus has fifteen electrons and sixteen neutrons

Answer 2

atomic no is equal to the no of protons or no of electrons 

therefore atomic no of element X is 15 

mass no is eual to sum of no of protons and no of neutrons 

there fore mass no = 15 + 16 
                                = 31