Chemistry Questions Essay

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1. The diagram below shows the electronic structure of boron. (a) The electrons are represented by arrows. What property of the electrons do these ‘up’ and ‘down’ arrows represent? (1) (b) Suggest why electrons which occupy the 2p sub-levels have a higher energy than electrons in the 2s sub-level. (1) (c) Complete the following energy level diagram to show the electronic structure of carbon. (2) (d) Explain the meaning of the term first ionisation energy. (2) (e) Explain why boron has a lower first ionisation energy than beryllium. (3) (f) Explain why the first ionisation energy of helium is very large. (1) (Total 10 marks) 2. (a) Explain why electrical conductivity decreases across Period 3 from sodium to phosphorus. (3) (b) Explain why atomic radius decreases across Period 3 from sodium to chlorine. (2) (c) The table below shows the melting temperatures, Tm, of the Period 3 elements. Element Na Mg Al Si P S Cl Ar Tm/K 371 923 933 1680 317 392 172 84 Explain the following in terms of structure and bonding. (i) Magnesium has a higher melting temperature than sodium. (2) (ii) Silicon has a very high melting temperature. (2) (iii) Sulphur has a lower melting temperature than magnesium. (2) (iv) Argon has a lower melting temperature than chlorine. (3) (Total 14 marks) 3. (a) Why are the elements sodium to argon placed in Period 3 of the Periodic Table? Describe and explain the trends in electronegativity and atomic radius across Period 3 from sodium to sulphur. (7) (b) Describe the trend in pH of the solutions formed when the oxides of the Period 3 elements, sodium to sulphur, are added separately to water. Explain this trend by reference to the structure and bonding in the oxides and by writing equations for the reactions with water. (19) (c) Describe and explain any

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