A 53. Let X represent the unknown nuclide. The reaction equation is Z A 1 0 4 X + n e+2 He . Z 0 -1 2 Conservation of charge yields Z +0 = -1+4 or Z =3. Conservation of mass number yields A+1 =0+8 or A =7. According to the periodic table in Appendix G (also see Appendix F), lithium has atomic 7 number 3, so the nuclide must be Li. 3