Question 1: Define an atom according to modern science.

Answer: An atom is the smallest unit of an element that retains the element's properties and consists of protons, neutrons, and electrons.

Question 2: Describe the main difference between Dalton's model and Thomson's 'plum pudding' model of the atom.

Answer: Dalton's model viewed the atom as a solid sphere with no internal structure, while Thomson's 'plum pudding' model proposed that the atom was a sphere of positive charge with embedded electrons.

Question 1: Calculate the number of neutrons in an atom of Uranium-238. (Atomic number of Uranium = 92)

Answer: 146

Question 2: An isotope has 15 protons and 16 neutrons. What is its atomic mass number?

Answer: 31

Question 1: Describe the safety precautions that should be taken when handling radioactive isotopes in a laboratory setting.

Answer: Use protective clothing, limit exposure time, work behind shielding, and follow proper disposal procedures for radioactive materials.

Question 1: A sample contains 10 protons, 10 electrons, and 12 neutrons. What is the atomic number and atomic mass of this element?

Answer: Atomic number = 10, Atomic mass = 22

Question 1: Explain how the discovery of the electron led to the development of the modern atomic model. Include key scientists and their contributions in your answer. (6 marks)

Answer: The discovery of the electron by J.J. Thomson in 1897 demonstrated that atoms are divisible and contain negatively charged particles. This led to the development of the 'plum pudding' model, where electrons were embedded in a positive sphere. Later, Rutherford's gold foil experiment revealed a small, dense nucleus, refining the atomic model to include a central nucleus. These discoveries shifted the view of atoms from indivisible spheres to complex structures with subatomic particles, ultimately leading to the modern quantum mechanical model.

Question 1: How is the understanding of atomic structure used in nuclear medicine?

Answer: Atomic structure knowledge allows for the use of radioactive isotopes in imaging and treatment, such as in PET scans and cancer radiotherapy.