Question

I have come to see you, the doctor, because I was feeling a bit ill. The first thing the nurse did was look at me and see I had a large growth in my neck. “Wow!” she said. “How long has this been going on?”    “For a couple of months”, I replied. After going through a bunch of tests, I was diagnosed with a goiter. This problem was historically treated with seaweed and is caused by a deficiency of iodine in the diet. The doctor prescribes iodine tablets. You, as the nurse, are faced with deciding which bottle of iodine I need. The doctor says I need Iodine-127. The supply person has made a mistake and put two different types of iodine on the shelf. I need Iodine-127. This is the heavier isotope of Iodine, the other being Iodine -126.

a)(1pt) Iodine is a diatomic element. Therefore, how would you represent elemental iodine in a chemical equation? Explain why you think it occurs in this way?

b)(4pts) Iodine-126 and Iodine-127 are isotopes of each other. Explain, in your own words, what an isotope is and write the complete chemical symbol for Iodine-126 and Iodine-127 and label what each number means

Answer 1

a)

the diatomic implies, two atoms, i.e. I-I is bonded so we express this as I2

This is much more stable than simply I, which has only 7 electrons in its valence, when I meets another I atom then they can form a single bond and have a full octect, which is very likely

therefore, this is much more stable

b)

isotope --> same atomic number, different mass number.

recall that atomic number = proton count

mass number 0 neutrons + proton

if protons are not changing, then the neutrons are changing.

for I = 126, atomic no. = 53

therefore, protons = 53

neutrons in 126 = 126-53 = 73

for I 127, there are 127-53 = 74 neutrons.