OCR A Jan 2011 Paper 1 Q1

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Answer all the questions. 1 Sir Humphrey Davy, the inventor of the miners safety lamp, was the first person to isolate the element strontium. Robert Bunsen, the inventor of the Bunsen burner, was partly responsible for the discovery of the element rubidium. Rubidium and strontium occur next to each other in the Periodic Table. A sample of rubidium was analysed and found to consist of two isotopes, rubidium-85 and rubidium-87. Information about these isotopes is given in the table. isotope relative isotopic mass abundance (%) rubidium-85 rubidium-87 85.00 87.00 72.15 27.85 (a) In terms of sub-atomic particles, what is the difference between these isotopes of rubidium?[1] (b) Define the term relative atomic mass.[3] (c) Calculate the relative atomic mass of the sample of rubidium. Give your answer to two decimal places. (d) Both rubidium, a Group 1 element, and strontium, a Group 2 element, have their outermost electrons in the 5s orbital. answer =[2] What 3-D shape is the 5s orbital?[1]OCR 2011<br />
 (e) Ionisation energies allow chemists to determine electron structures. The first two ionisation energies of rubidium and strontium are shown in the table. element rubidium strontium first ionisation energy / kJ mol1 second ionisation energy / kJ mol1 403 550 2632 1064 (i) Write an equation to represent the second ionisation energy of strontium. Include state symbols.[1] (ii) Why is the first ionisation energy of strontium larger than the first ionisation energy of rubidium? In your answer you should use appropriate technical terms spelled correctly.[3] (iii) Why is the second ionisation energy of rubidium larger than the second ionisation energy of strontium?[2]OCR 2011 [Total: 13] Turn over<br />

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