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SCH3U Matter, Chemical Trends and Bonding Trends in the Periodic Table In this exercise, you will construct three different graphs to obtain a pictorial representation of the changes in three properties of the elements as their atomic number increases. By plotting these properties, you should see that elements are grouped within the periodic table according to similarities in these properties. The three properties are atomic radius, ionization energy, and electronegativity. Atomic Radius The atomic radius of an atom is the distance from the centre of the atom to the outermost shell that contains electrons. A convenient unit for this distance is the picometer, which is one/one trillionth of a meter (1 x 10-9 m). Ionization Energy The ionization energy of an atom is the amount of energy (in kilojoules) that is required to remove one of the outermost electrons from the atom. In other words, the energy needed to strip an electron away from the atom. Electronegativity The electronegativity of an atom is a measure of the ability of the atom to attract an electron from another atom. If an atom is really good at ‘stealing’ electrons from another atom, then it has a high electronegativity value. The Noble Gas elements do not have electronegativity values since they are stable with full outer energy levels. Procedure: For each set of data... 1. Turn the graph paper sideways so that the long side becomes the X-axis. The X-axis is the Atomic Number for all graphs and should take up the whole side of the paper. 2. Label the Y-axis with the given property and establish a scale that begins with ‘0’. 3. Graph the data below. 4. Label each point with the corresponding element symbol. 5. At atomic numbers 2(He), 10(Ne) and 18(Ar) draw a red vertical line through the graph. This separates the plot into four sections. Label the sections 1 – 4. 6. In each section, draw a curve of best fit among the points. DO NOT play connect the dots!! 7. Include a title. Atomic Radius for the First 20 Elements Atomic Number 1 2 3 4 5 6 7 8 9 10 Atomic Radius (picometers) 37 32 152 111 79 77 74 76 71 69 Atomic Number 11 12 13 14 15 16 17 18 19 20 Atomic Radius (picometers) 186 160 143 117 110 102 100 97 227 197 Ionization Energy for the First 20 Elements Atomic Number 1 2 3 4 5 6 7 8 9 10 Ionization Energy (kJ/mol) 1294 2336 511 886 787 1071 1380 1294 1656 2048 Atomic Number 11 12 13 14 15 16 17 18 19 20 Ionization Energy (kJ/mol) 486 725 569 775 1046 985 1236 1496 408 581 Electronegativity Values for the First 20 Elements Atomic Number 1 2 3 4 5 6 7 8 9 10 Electronegativity 2.1 No Value 1.0 1.5 2.0 2.5 3.0 3.5 4.0 No Value Atomic Number 11 12 13 14 15 16 17 18 19 20 Electronegativity 0.9 1.2 1.5 1.8 2.1 2.5 3.0 No Value 0.8 1.0 Questions - Please answer with complete sentences. Atomic Radius 1. According to the graph, what happens to the radius (size) of an atom as you move across a Period (row) of the Periodic Table? 2. According to the graph, what happens to the radius (size) of an atom as you move down a Group (column) of the Periodic Table? Ionization Energy 1. Generally, what happens to the ionization energy of an atom as you move across a Period of the Periodic Table? 2. Generally, what happens to the ionization energy of an atom as you move down a Group of the Periodic Table? 3. How are these trends different that those seen for Atomic Radius? Electronegativity 1. Generally, what happens to the electronegativity of an atom as you move across a Period? 2. Generally, what happens to the elctronegativity of an atom as you move down a Group? 3. How are these trends different that those seen for Atomic Radius?