Final answer:
A neutral iodine atom has 53 electrons. When iodine is an anion with a 1- charge, known as iodide, it has 54 electrons. Iodine's mass number is 127, leading to 74 neutrons in the atom.
Step-by-step explanation:
The number of electrons in a neutral iodine (I) atom is equal to the atomic number, which is 53. This means a neutral iodine atom has 53 electrons. However, when iodine is present as an anion with a 1- charge, the number of electrons increases by one to accommodate the extra negative charge. Therefore, in an iodide ion (I-), there are 54 electrons. The mass number of iodine is 127, and since the sum of the numbers of protons and neutrons equals the mass number, the number of neutrons can be calculated as 127 - 53 = 74. Thus, an iodide ion has 53 protons, 74 neutrons, and 54 electrons.