Indium nuclides

Indium-107 atoms undergo a positron emission and an electron capture before they reach a stable nuclide. What is the final product ... 

Indium is widely distributed in small quantities in ores together with tin, lead, zinc, manganese, and antimony making its occurrence in the terrestrial core to be about 1 part in 10. The naturally occurring isotopes of indium are " In, 4.33% and " In, 95.67%, and indium has over 30 radioactive nuclides. 

Write the correct symbol, with both superscript and subscript, for each of the following. Use the fist of elements on the front inside cover as needed (a) the nuclide of hafnium that contains 107 neutrons (b) the isotope of argon with mass number 40 (c) an a particle (d) the isotope of indium with mass number 115 (e) the nuclide of silicon that has an equal number of protons and neutrons. 

Tin-112 is a stable nuclide, but indium-112 is radioactive, with a half-life of only 14 min. How can we ejqjlain this difference in nuclear stability ... 

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