2. Neon (10Ne) has three stable isotopes with consecutive mass numbers. Write th

Question

2. Neon (10Ne) has three stable isotopes with consecutive mass numbers. Write the complete nuclear symbol (with neutron number) for each. (Enter your answer in the form AZX_{N}. Separate substances in a list with a comma.)

3. A thyroid cancer patient is given a dosage of 131I (half-life = 8.1 d). What fraction of the dosage of 131I will still be in the patient's thyroid after 64.8 days? (Let N0 and Nf represent the initial dose and the amount left after 64.8 days, respectively. Enter your answer as a fraction.)
Nf/N0 =

Explanation / Answer

1. average atomic mass of bromine =

fraction of 79 Br = 22.36/100 = 0.2236

fraction of 81 Br = 77.64/100 = 0.7764

79Br atomic mass = 78.918 u

81Br atomic mass = 80.916 u

average atomic mass of bromine(Br) = 0.2236*78.918+0.7764*80.916

= 80.45 u

2.      2010Ne , 2110Ne , 2210Ne

3. T1/2 = 0.693/k

K = 0.693/8.1 = 0.085 day^-1.

k = (2.303/t)log(1/a-x)

0.085 = (2.303/64.8)log(1/a-x)

a-x = 0.004

fraction of the dosage of 131I will still

be in the patient's thyroid after 64.8 days = 0.004

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