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Periodic Trends Name______________ Hr___ A. Use the periodic table, your notes and your knowledge of periodic trends to answer the following questions. 1. Define atomic radius 2. Why does atomic radii decrease as you move across a period? 3. Which atom in each pair has the larger atomic radius? a.__K__ Li or K b.___Ca_ Ca or Ni c.____Ga Ga or B d.____O O or C e.____Br Cl or Br f._Ba___ Be or Ba g.___Si_ Si or S h.____Au Fe or Au 4. Which ion in each pair has the smaller atomic radius? Helps if you compare how many protons vs electrons each in has. More protons can tug on the electrons, remember? a.____ K+ or O2b.____ Ba2+ or Ic.__Al__ Al3+ or P3- 5. Define the term electronegativity. What element has the greatest EN and why? What elements have NO EN and why? Ability to attract electrons from another atom. F has greatest as it has the shortest distance between protons and outer electrons = greatest coulumbic attractive force. 6. How is EN related to reactivity? Elements with High EN are very reactive. 7. Which atom in each pair has the higher electronegativity? a._O___ Ne or O b.__Be__ Ba or Be c.__F__ Ar or F d._Cu___ Rn or Cu e._I___ I or Kr f.___H_ H or He 8. Define “ionization energy (same as ionization potential). As you go down a column of elements on the PT (Li to Na to K, etc), what is the trend for IE? How did we “see” the alkali metal demo with sodium and potassium? How much energy needed to remove an electron. Increases down the column; potassium much more reactive than sodium and is lower in the column. 9. Which atom in each pair has the lower first ionization energy? a._Na___ Na or O b._Ba___ Ba or Be c.__F__ Ar or F d.__Cu__ Ra or Cu e.__I__ I or Ne f.__K__ K or V B. Answer each of the following. Support your answer with reasons. 1. Chlorine, selenium and bromine are located near each other on the periodic table. Which of these elements is (a) the smallest atomic radius? Cl (b) the atom with the lowest ionization energy? Cl or Se 2. Phosphorus, sulfur, and selenium are located near each other on the periodic table. Which of these elements is (a) the smallest atomic radius? S (b) the atom with the highest EN and S(c) is the most reactive? S 3. Scandium, yttrium, and lanthanum are located near each other in the periodic table. Which of these elements is (a) the largest atomic radius? La (b) the atom with the smallest ionization energy La and (c) is the most reactive? La 4.Which of the following is the smallest: a lithium atom, a lithium ion with a charge of +1, or a sodium atom? Li ion – fewer electrons to pull on so radius is shorter 5.Which of the following is the largest: a tellurium ion with a charge of –2, an iodine ion with charge of –1 or a xenon atom? Te more electrons than protons 6.Aluminum, silicon, and phosphorus are located near each other in the periodic table. Which of these elements is (a) the largest atomic radius? Al (b)the atom with the highest EN P and (c) is the most reactive? P 7 – 11 Write the electron configuration for each element. Determine how many electrons there are in the outer ring. Determine if it will have high or low EN, high or low IP. Electron config Outer ring? High or low IP? Sodium High or low EN? Low Chlorine High High Calcium Low Low Oxygen High High Aluminum mid mid Low Using the data in the table above, provide an argument explaining why sodium is so much more reactive than calcium. Using the data in the table above, provide an argument explaining why both oxygen and chlorine are very reactive gases.