1 Write the correct symbol, with both superscript and subscript,
for each of the following. Use the list of elements in the front
inside cover as needed: (a) the isotope of platinum that contains
118 neutrons, (b) the isotope of krypton with mass number 84,
(c) the isotope of arsenic with mass number 75, (d) the isotope of
magnesium that has an equal number of protons and neutrons.