Question

Fermium-253 is a radioactive isotope of fermium that has a half-life of 3.0 days. A scientist obtained a sample that contained 216 micrograms of fermium-253.
Complete the table to show how much fermium-253 should remain in the sample at the indicated times after the scientist obtained the sample.

Answer 1

Problem 2

You start out with 216 ugrams of Fermium - 253. After 3 days, you will have 1/2 as much. 108 ugrams is what you have.

Another 3 days goes by. You started with 108 ugrams. That gets cut in 1/2 again. Now you have 54 ugrams.

Finally another 3 days goes by. You started with 54 ugrams. you now have 1/2 as much which would be 27 ugrams

#days              Amount in micrograms

0                              216

3                               108

6                                54

9                                27

Problem One

You are using Nitrogen as your base example. The first thing you should do is fill in the table. Then you should try and make some rules. You need the rules in case the exam you are preparing for picks a different element to talk about these bond tendencies. In any event, it's handy to think this way.

Table

Bond               Energy Kj/Mol               Bond Length pico meters

N - N                 167                                                145

N=N                  418                                                125

N≡N                  942                                               110

Rules

As the number of bonds INCREASES, the energy contained in the bond goes UP

As the number of bonds INCREASES, the length of the bond goes DOWN.

Answer 2

1. Radioactive decay

The half-life of Fm-198 (3.0 days) is the time it takes for half the Fm to decay.  

After one half-life, half (50 %) of the original amount will remain.

After a second half-life, half of that amount (25 %) will remain, and so on.

We can construct a table as follows:

 No. of                   Fraction         Amount

half-lives  t/days  remaining   remaining/µg

       1          3.0             ½                  216

       2         6.0             ¼                  108

       3         9.0             ⅛                    54

2. Bond length and bond energy

The bond order of a bond is the number of bonding electrons between the two nuclei.

As the number of bonding electrons increases, the nuclei are pulled more tightly together (the bond energy increases) and the bond length decreases.

We can construct a table as follows:

Bond  Bond energy/kJ·mol⁻¹  Bond length/pm

N-N                 167                                 145

N=N                 418                                 125

N≡N                 942                                 110