Technetium-99 has a half life of 8 hours. How much of a 100 gram sample is undecayed after 16 hours?

50g

Explanation:

The half - life of a radioactive material is the time taken for half of a material to decay by half or into half.

The faster the half life the faster the rate of this decay and vice versa.

 Now if initially we have 100g of a Technetium - 99;

If the half - life is 8hrs, at every 8 hours, the mass of technetium will decay by half;

 So;       at 16hrs, the mass of the material will be 50g

float.

archimedes' principle

denser than water sinks in water.

denser than mercury would sink in it

at right angles to each other