During electron capture, an atomic electron is captured by a proton in the nucleus. The stable nuclide thallium-205 (Tl) can be formed when an unstable lead (Pb) nuclide captures an electron. 3 (b) (c) Write down the equation to represent this decay. 83-8 The neutron number and the proton number Z are not equal for the nuclide TI. Explain, with reference to the forces acting within the nucleus, the reason for this. Thallium-205 (Tl) can also form from successive alpha (a) and beta-minus (B) decays of an unstable nuclide. The decays follow the sequence a a. The diagram shows the position of 20 Tl on a chart of neutron number against proton number. 81 neutr www. 132- 120- 128- 124- 122- 120- 118 100M on under 12 Draw four arrows to show the sequence of changes to # and Z that occur as the 205Tl forms from the unstable nuclide. 81