Question

is the amount of time required for one - half of a sample of a radioactive substance to decay.
a decay series
b half - life
c 2 years
or radioactive substances have a half - life.
a unstable
b most elements
c transition metals

Explanation:

The half - life is defined as the time required for one - half of a sample of a radioactive substance to decay. Also, most radioactive substances are unstable and have a half - life.

Answer:

1. B. Half life
2. A. Unstable