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Name:Date:Period:DISCOVERING PERIODIC TRENDS aka THE STRAW LAB (50 pts)INTRODUCTION:A trend is a predictable change in a certain direction. The arrangement of the periodic table reveals trends in the properties of the elements. Understanding periodic trends allows us to make predictions about the chemical behavior of the elements. In this activity, we will explore the properties of atomic radius, ionic radius, ionization energy, and electronegativity,. Your team will use a pegboard and straws of different lengths to make a 3D model of one of the periodic trends. Your classmates are also assigned a trend to model, but a different one from you. Remember that the Periodic Table is not as simple as it seems—there are trends both horizontally (across a period) as well as vertically (down a family). We will not only examine these trends, but also explore the chemical explanations for these trends. At the end of the activity you will examine all of the models of the trends and answer a series of questions.PRE-LAB QUESTIONS (20 pts):1. Vertical columns on the periodic table represent (circle one)PERIODS / GROUPSWhat do we know about vertical columns and valence electrons, chemical properties, and how the elements will react?2. Horizontal rows on the periodic table represent (circle one)PERIODS / GROUPSWhat do we know about horizontal rows and valence electrons, chemical properties, how the elements will react, and occupied energy levels?Look in the RED book at pages 187-194 and find definitions (include drawings) for:3. Atomic Radius 4. Shielding (pg. 188)5. Ions 6. Ionic Radius 7. First Ionization Energy 8. Second, Third, etc Ionization Energy 9. Octet Rule10. Electronegativity MATERIALS:CalculatorElement Data TableMetric RulerPlastic StrawsPegboardScissorsPROCEDURE:Form four working groups. Your group to be assigned one of the following element properties: atomic radius, ionic radius, ionization energy, or electronegativity.Obtain an Element Data table with your assigned property, a pegboard, a metric ruler, scissors, and 42 plastic straws.Find the maximum value of the property for the 42 main group elements in periods 1-6. Example: The maximum value of the electronegativity for these elements is 4.0 Paulings (for fluorine).Let the length of the straw minus one cm represent this maximum value. This length will be the scale for all the other values of your given property of the elements.Example: For a straw that is 19.0 cm long, a straw length of 18.0 cm will represent an electronegativity of 4.0 Paulings. The scale is thus 18.0 cm = 4.0 Paulings. Round off the straw length to 0.1 cm (1 mm).Using this "straw" scale as a ratio, calculate the straw length that is needed to represent the assigned property for each element in the list.Example: The electronegativity of phosphorus is 2.1 Paulings. Therefore, a straw length of 9.45 cm is needed to represent the electronegativity of phosphorus. Round off all straw lengths to 0.1 cm.Add 1.0 cm to the calculated straw length for each element and cut a straw to that length.Example: Cut a straw 10.5 cm long (9.5 cm + 1.0 cm) to represent phosphorus.Place the straw in the pegboard according to the position of the element in the periodic table. (Remember, the transition elements are not included in the list of representative elements.)Repeat steps 5-8 above for each element on the list.LABORATORY QUESTIONS (20pts): To answer the questions, visit all the stations to discover the trends! Refer to the RED book for help.Atomic RadiusDescribe and indicate on the drawing to the right the general trend in atomic radius across a period.Why does this trend make sense in relation to the attraction between subatomic particles and shielding within the atom?Describe the general trend in atomic radius down a group/family. Why does this relationship make sense in relation to energy levels on the periodic table?Ionic RadiusWhat happens to the radius of an atom when it becomes a positive ion (or cation)? Why?Describe and indicate on the drawing to the right the general trend in ionic radius amongst the positively charged ions or cation across a period?What happens to the radius of an atom when it becomes a negative ion (or anion?) Why?Describe and indicate on the drawing to the right the general trend in ionic radius amongst the negatively charged ion or anion across a period?Ionic Radius (cont)Which elements are missing ionic radius values? Why?Describe the general trend in ionic radius down a group/family. Ionization EnergyDescribe and indicate on the drawing to the right the general trend in ionization energy across a period.Why does this trend make sense in relation to the atomic radius trend?Describe the general trend in ionization energy down a group/family.Why does this trend make sense in relation to the atomic radius trend?Electro negativityDescribe the general trend in electronegativity across a period.Why does this trend make sense in relation to the octet rule? Describe the general trend in electronegativity down a group/family.Why does this trend make sense in relation to atomic radius or size?Which elements are missing electronegativity values? Why?Concluding questions (10 pts):Which has the largest atomic radius: magnesium, silicon, sulfur, or sodium? The smallest?Determine which element in each pair has the largest atomic radius:Element in period 2, group 1 or the element in period 3, group 18Element in period 5, group 2 or the element in period 3, group 16Element in period 3, group 14 or the element in period 6 group 15An element forms a negative ion when ionized. What group numbers might this element be in? Explain.Of the elements magnesium, calcium, and barium, which forms the ion with the largest radius? The smallest?Which element has the larger ionization energy?Li or NKr or NeCs or LiWhich element in the pair is more electronegative?K or AsN or SbSr or BeIndicate whether fluorine or bromine has a larger value for each of the following properties?atomic radiusionic radiusionization energy electro negativity ................
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