OCR A Jun 2013 Paper 1 Q1

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Answer all the questions. 1 Silicon and potassium are two elements found in the Earths crust. (a) Silicon and potassium both exist as several isotopes. (i) Define the term relative isotopic mass.[2] (ii) Complete the table below for an atom and an ion of two different isotopes of potassium. Protons Neutrons Electrons 39K22 19 18 (b) Complete the electron configuration of a silicon atom. 1s2[1] (c) (i) Silicon reacts with chlorine to form molecules of silicon tetrachloride, SiCl4. How many molecules are present in 8.505 g of SiCl4? [2]OCR 2013 answer =molecules [3]<br />
 (ii) Potassium reacts with chlorine to form an ionic lattice of potassium chloride, KCl. A diagram of part of the potassium chloride lattice is shown below. Add labels to each circle in the diagram to show the particles present in the lattice. The diagram assumes all particles have the same size. [2] [Total: 10]OCR 2013 Turn over<br />

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