Final answer:
The mass number of the ion with 105 electrons, 159 neutrons, and a +1 charge is 263.
Step-by-step explanation:
The mass number of an ion is the sum of the number of protons and neutrons in the nucleus. To find the mass number of the ion, you need to add the number of protons (which is equal to the charge of the ion) and the number of neutrons.
In this case, the ion has 105 electrons, so the number of protons is 105 - 1 = 104. The number of neutrons is given as 159. Adding the protons and neutrons together, the mass number of the ion is 104 + 159 = 263.
Therefore, the mass number of the ion is 263.