Question
A nucleus of americium-241 has the nuclide notation shown.
\(^{241}_{95}\) Am
(a) (i) Determine the number of neutrons in a nucleus of americium-241.
number of neutrons =…………………………………………………………………………………………….
(ii) Determine the charge on a nucleus of americium-241.
charge =………………………………………………………………………………………………….
(b) Americium-241 decays by emitting α-particles.
Put a tick in the box next to each correct statement.
(c) Americium-241 has a half-life of 432 years.A sample contains 16 mg of americium-241.Calculate the time it takes until only 4.0 mg of americium-241 are left in the sample.
time = ………………………………………. years
Answer/Explanation
Answer:
(a)
(i) 146
(ii) positive
95
(b) tick in 3rd box
tick in 4th box
(c) idea of 2 half-lives
(432 × 2) = 864 (years)
Question
Astatine-210 is a radioactive material. The nucleus of astatine can be represented by the symbol shown.
\(^{210}_{85}\)At
(a) Complete the table to describe the nucleus of astatine-210.
|
type of particle |
number of particles |
charge on particle |
|
neutron |
||
|
positive |
(b) Astatine-210 has a half-life of 8 hours.
(i) The count rate of a sample of astatine-210 is measured over 24 hours.
On Fig. 12.1, sketch a line to show how the count rate changes over the 24 hours.
(iii) The mass of a sample of astatine-210 is 0.500 kg.
Calculate how long it takes for 0.375 kg of the sample to decay.
decay time = ……………………………………….. hours
Answer/Explanation
Answer:
(a) (neutron) – 125 – neutral
proton(s) – 85 – (positive)
(b)(i) curve of negative gradient, gradient decreasing
curve with negative gradient starts on y axis
(b)(ii) 0.125 (kg) (remaining)
two half-lives indicated
16 hours