A radioactive nucleus emits an alpha (α) particle. What happens to its mass number?

Half-life is defined as the time taken for:

Which type of radioactive decay does NOT change the proton number (atomic number)?

A sample has an activity of 800 Bq. After 2 half-lives, the activity will be:

Background radiation must be measured and subtracted from readings because:

Complete the nuclear equation for the beta-minus (β⁻) decay of Iodine-131: ¹³¹₅₃I → _____ + β⁻ (a) State the mass number of the product nucleus. [1] (b) State the proton number of the product nucleus. [1] (c) Identify the element formed (use a periodic table if needed). [1]

A radioactive sample has a half-life of 20 minutes. The initial count rate is 2000 counts per minute. (a) Calculate the count rate after 1 hour. Show your working. [3] (b) Explain why the count rate never reaches exactly zero. [2]

Explain what happens inside the nucleus during beta-minus (β⁻) decay. Your answer should include: • What particle changes • What it changes into • What is emitted [3]

A student measures the activity of a radioactive source at different times: Time (min) | Activity (Bq) 0 | 960 15 | 480 30 | 240 45 | 120 (a) Use the data to determine the half-life of the source. [2] (b) Predict the activity at 60 minutes. [2]

Complete the nuclear equation for alpha (α) decay of Radium-226: ²²⁶₈₈Ra → ²²²₈₆Rn + _____ (a) State what the blank should contain (symbol and numbers). [2] (b) Name the particle emitted. [1]

A student investigates radioactive decay using a Geiger-Müller (GM) tube and counter. The graph shows activity vs. time.

A student sets up apparatus to measure background radiation: • GM tube connected to counter • No radioactive source present • Counter reading: 42 counts in 10 minutes (a) Calculate the background count rate in counts per minute. [2] (b) Later, with a source present, the counter reads 186 counts per minute. Calculate the actual activity of the source. [2]

A student plots a decay curve but makes an error - they plot "number of nuclei remaining" instead of "activity". (a) Explain why the graph shape would still show the same half-life. [2] (b) State one safety precaution when handling radioactive sources. [1]

A teacher demonstrates the randomness of radioactive decay using a GM tube and a weak source. The count rate over 10-second intervals is: 18, 22, 15, 19, 24, 16, 21, 17 (a) Calculate the mean count rate. [2] (b) Explain why the count rate varies between intervals even though the half-life is constant. [2]

A student measures the count rate of a source at regular intervals. Their results table shows: Time (s) | Count Rate (cpm) | Corrected Count Rate (cpm) 0 | 324 | 320 30 | 164 | 160 60 | 84 | 80 90 | 44 | 40 (a) State what correction the student made. [1] (b) Use the corrected values to show the half-life is 30 seconds. [2] (c) Suggest why using corrected values is more accurate for determining half-life. [2]