Answer: 52 protons.
Step-by-step explanation:
Using the periodic table, we find Sn under group 14 in period 5 (i.e., 14th column, 5th row). Sn has an atomic number of 50, which means it normally has 50 protons and 50 electrons (normally, its net charge is 0).
If, Sn somehow has a net charge of +2, then it must have more protons than normal. In fact, it must have exactly 2 more protons than normal. Since 52 - 50 = 2.
So, if Sn has a net charge of +2, then it must contain 52 protons.