Answer
${^{79}_{34}Se}$
Work Step by Step
The element that has 34 protons in its nucleus is Selenium (Se) . We find this in periodic table of the elements, as atomic number (Z) is given in this table. ( Z is the number of protons).
Mass number is the total number of protons and neutrons. In this case it is 79 ( 34 + 45).
So the nuclide symbol for the nucleus that contains 34 protons and 45 neutrons, should be ${^{79}_{34}Se}$ .
