Technetium-99m is an ideal radioisotope for scanning organs because it has a half-life of 6.0 h and is a pure gamma emitter. Suppose that 84.1 mg were prepared in the technetium generator this morning. How many milligrams of technetium-99 m would remain after the following intervals?

Full Question: Technetium-99m is an ideal radioisotope for scanning organs because it has a half-life of 6.0 h and is a pure gamma emitter. Suppose that 84.1 mg were prepared in the technetium generator this morning. How many milligrams of technetium-99 m would remain after the following intervals?

Options:

- One half life

- Two half lives

- 18h

- 24h

a) 42.05mg

b) 21.025mg

c) 10.5125mg

d) 5.25625mg

Explanation:

Half life = 6h

Initial Amount = 84.1mg

Before proceeding further;

The half life  a material is simply the amount of time it takes for half of that material to decay.

a) One half life

84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)

b) Two half lives

84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)

42.05mg --> 42.05mg / 2 = 21.025mg (Second Half life)

c) 18h

This is the same as three half lives because; 3 * 6 = 18

84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)

42.05mg --> 42.05mg / 2 = 21.025mg (Second Half life)

21.025mg --> 21.025mg / 2 = 10.5125mg (Third Half life)

d) 24h

This is the same as four half lives because; 4 * 6 = 24

84.1mg --> 84.1mg / 2 = 42.05mg (First Half life)

42.05mg --> 42.05mg / 2 = 21.025mg (Second Half life)

21.025mg --> 21.025mg / 2 = 10.5125mg (Third Half life)

10.5125mg --> 10.5125mg / 2 = 5.25625mg (Fourth Half life)