Periodicity Review
Periodicity Review Metals, non-metals & metalloids: Periodicity Review Physical Properties Atomic Radius Periodicity Review Physical Properties Ionic Radius Periodicity Review Physical Properties Ionization Energy – minimum amount of energy required to strip away one electron from an atom of that element in the gaseous state, producing a positive ion (cation) Periodicity Review Ionization Energy Periodicity Review Physical Properties Electronegativity – the ability of an atom to attract electrons in a chemical bond Periodicity Review Physical Properties Melting Point melting points for period 3 elements (C): 98 649 660 1410 44 119 –101 –189 Na Mg Al Si P4 S8 Cl2 Ar Periodicity Review Melting Points: Periodicity Review Melting Point within a group: M.P. decreases down a group for metals (weaker metallic bonding due to more shielding) M.P. increases down a group for halogens (greater mass greater van der Waal’s forces) Periodicity Review Periodicity Review Chemical Properties Elements in the same group have similar chemical properties, due to same # of valence electrons. Alkali Metals: soft, silvery metals, easily cut with a knife, very reactive with air & water. Periodicity Review Alkali metals react with water to form a base and hydrogen gas: 2Na + 2H2O 2NaOH + H2 Reactivity increases down the group due to larger radii lower ionization energies Periodicity Review Alkali metals react easily with halogens to form halides (ionic salts): 2Na + Cl2 2NaCl Periodicity Review At room temperature: fluorine is a pale yellow gas; chlorine is a yellow-green gas; bromine is a reddish brown liquid; iodine is a shiny black solid that sublimes readily Periodicity Review Periodicity Review Halogen reactions with halide ions: Whenever the aqueous halogen reacts with another halide ion that is a weaker oxidizing agent, that halogen (the weaker oxidizing agent) is formed. Cl2(aq) + 2Br–(aq) 2Cl–(aq) + Br2(aq) Cl2(aq) + 2I–(aq) 2Cl–(aq) + I2(aq) Cl2(aq) + 2F–(aq) NR Periodicity Review Metallic nature decreases across a period (left to right). Metallic nature increases down a group. Periodicity Review Note acidity of period 3 oxides: Periodicity Review Metal oxides are basic in solution: Na2O(s) + H2O(l) NaOH(aq) (Na+(aq) + OH–(aq)) MgO(s) + H2O(l) Mg(OH)2(aq) (Mg+2(aq) + 2OH–(aq)) NaOH is more basic than Mg(OH)2 (Na2O is more basic in aqueous solution than MgO) Periodicity Review Non-metal oxides are acidic in solution: P4O6(g) + 6H2O(l) 4H3PO3(aq) P4O10(g) + 6H2O(l) 4H3PO4(aq) H3PO3 has a pKa of 2.00 H3PO4 has a pKa of 2.15 So H3PO3 is a slightly stronger acid (thus P4O6 is a slightly more acidic oxide). Periodicity Review SO2(g) + H2O(l) H2SO3(aq) SO3(g) + H2O(l) H2SO4(aq) H2SO4 (pH 0 for 1M solutions) is a slightly stronger acid than H2SO3 (pH 1 for 1M solutions). Both are stronger acids than those formed from the phosphorus oxides. Periodicity Review Cl2O(g) + H2O(l) 2HClO(aq) Cl2O7(g) + H2O(l) 2HClO4(aq) Perchloric acid is a strong acid (pH 0 for 1M solutions) – much stronger than hypochlorous acid. Therefore, Cl2O7 is a much more acidic oxide of chlorine in aqueous solution. Periodicity Review Oxides of metalloids are typically amphoteric in solution (producing both acids & bases). However, in the case of 3rd period oxides, it is actually aluminum oxide that is amphoteric. Don’t worry about the particular reactions – just know that Al2O3 is amphoteric. Periodicity Review Silicon (the metalloid in period 3) exists commonly in nature as silicon dioxide (SiO2), which is actually very weakly acidic, reacting with very strong bases. Periodicity Review Explain why the melting point of the elements increase in the order: sodium < magnesium < aluminum < silicon Periodicity Review The ionisation energies (IE) for the successive removal of the first four electrons of an element were determined to be: 732 kJ mol–1 1442 kJ mol–1 7683 kJ mol–1 10559 kJ mol–1 (a) Account for the fact that the IE value for each electron is larger than the previous one. (b) Describe how these values can be used to determine the electron configuration of the element involved. (c) To what periodic family does this element belong? (d) Account for the fact that the ionisation energies of the noble gases are higher than those of the elements immediately before and immediately after them on the Periodic Table. Periodicity Review Sodium and chlorine both react with water. (a) Write an equation for the reaction between sodium and water and state whether the resulting solution is acidic, neutral or alkaline. (b) Write an equation for the reaction between chlorine and water and state whether the resulting solution is acidic, neutral or alkaline. (c) Li, Na and K react with water. Which of the three reactions will be the most vigorous? Explain this at an atomic level. Periodicity Review (1) The early periodic tables were developed by correlating the physical and chemical properties of the elements with their respective atomic masses. (a) List one chemical and one physical property which leads to the grouping together of Lithium, sodium and potassium Chlorine, bromine and iodine Helium, neon and argon [6] (b) What feature of atomic structure underlies the modern basis of the periodic table? [1] Periodicity Review (2)(a) How does the physical state of the halogens vary from fluorine to iodine? Explain any variations noted. [3] (b) Discuss the reactions of the halogens (Cl2, Br2, I2) with halide ions (Cl–, Br–, I–). Include ionic equations as appropriate. Describe and account for any colour changes that take place. [4] Periodicity Review (3)The table to the right lists the first, second, and third ionisation energies (in kJmol–1) of six successive elements in the periodic table. ELEMENT 1 2 3 4 5 6 1st I.E. 2nd I.E. 1060 1900 1000 2260 1260 2300 1520 2660 418 3070 590 1150 3rd I.E. 2920 3390 3850 3950 4600 4940 Periodicity Review (a) Define the term ionisation energy of an element. [1] (b) For an element M write equations to represent 1st, 2nd, and 3rd ionisation energies. [3] (c) Which of the elements in the table is most likely to be an alkaline earth metal? Explain your answer. [2] (d) Which element is most likely to be an inert gas? Explain your answer. [2] (e) Suggest the names of a set of elements that could possibly represent the elements 1 to V1. [1] Periodicity Review (6) (a) State how the first ionisation energy varies down group 1. (b) Li, Na, and K react with water. Which of the three reactions will be the most vigorous? Explain this at an atomic level. (c) State whether the second ionisation energy of sodium is less than, the same as, or greater than the first ionisation energy. Explain your answer. Periodicity Review (7) The values of atomic radius and ionic radius for the period 3 elements are given below. Symbol of element Na Mg Al Si P S Cl Atomic radius / 10-12 m 186 160 143 117 110 104 99 Ionic radius / 10-12 m 65 45 42 212 190 181 98 Periodicity Review (a) Explain why the atomic radius decreases from sodium to chlorine.[2] (b) The ionic radius of aluminium is smaller than its atomic radius. The ionic radius of phosphorus is greater than its atomic radius. Explain the large difference in ionic radius between aluminium and phosphorus. [2] Periodicity Review (8) (a) State the meaning of the term electronegativity. [1] (b) State and explain the trend in electronegativity across period 3 from Na to Cl. [2] (c) Explain why Cl2 rather than Br2 would react more vigorously with a solution of I–. [2] Periodicity Review Periodicity Review Periodicity Review (11) Table 9 of the Data Booklet gives the atomic and ionic radii of elements. State & explain (a) the difference between the atomic radius of nitrogen and oxygen. [2] (b) the atomic radius of nitrogen and phosphorus. [1] (c) the atomic and ionic radius of nitrogen. [2]
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