Question 1: Define isotopes and describe how they differ from each other.

Answer: Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons.

Question 2: Explain why isotopes of an element have similar chemical properties but different physical properties.

Answer: Because they have the same electronic structure but different masses due to differing neutron numbers.

Question 1: Calculate the relative atomic mass of an element that has 75% of its isotopes with a mass of 23 u and 25% with a mass of 24 u. Show your working.

Answer: Relative atomic mass = (0.75 × 23) + (0.25 × 24) = 17.25 + 6 = 23.25 u

Question 2: An isotope of carbon has 6 protons and 8 neutrons. What is its atomic number and mass number?

Answer: Atomic number = 6, Mass number = 14

Question 1: Describe a safe method to handle radioactive isotopes in a laboratory setting, including safety precautions.

Answer: Handle radioactive isotopes using tongs and protective shielding, wear lab coats and gloves, work behind lead screens if necessary, and follow proper disposal procedures to minimise exposure.

Question 2: Identify the variables that need to be controlled in an experiment measuring the ratio of isotopes in a sample.

Answer: Variables include temperature, sample purity, measurement time, and instrument calibration.

Question 1: A sample of uranium contains 99.3% of isotope U-238 and 0.7% of isotope U-235. Calculate the average atomic mass of uranium in this sample. Show your working.

Answer: Average atomic mass = (0.993 × 238) + (0.007 × 235) = 236.19 + 1.645 = 237.835 u

Question 1: Explain how isotopic analysis can be used to determine the age of archaeological samples. (6 marks)

Answer: Isotopic analysis involves measuring the ratio of parent to daughter isotopes in a sample. By knowing the half-life of the radioactive isotope, scientists can calculate the time elapsed since the sample's formation, thus determining its age. This method is used in radiocarbon dating for organic materials and other techniques for different materials.

Question 2: Multiple choice: Which of the following statements about isotopes is TRUE?

Answer: They have different numbers of neutrons.

Question 3: Fill in the blank: The atomic number of an isotope is determined by the number of __________ in the atom.

Answer: protons

Question 1: Explain how radioactive isotopes are used in medical diagnostics and treatments.

Answer: Radioactive isotopes like technetium-99m are used in imaging to diagnose conditions, while others such as iodine-131 are used in treatment of thyroid disorders by targeting specific tissues.

Question 2: Discuss the role of isotopic analysis in environmental studies, such as tracking pollution or climate change.

Answer: Isotopic analysis helps trace sources of pollution by identifying unique isotopic signatures. It also allows scientists to study climate change by analysing isotopic ratios in ice cores and sediments, revealing historical environmental conditions.