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FROM FRIDAY….. Ionization Energy:
Checklist: ___ Trend is stated ___ Shielding ___ Nuclear charge ___ Highest filled orbital ___ Coulomb’s Law (optional) Ionization Energy: Using your “arsenal” of definitions from yesterday, come up with what you think the trend would be across a row and down a column. Work with your table and create a blank periodic table with arrows showing the general trend. Also write an explanation for each trend that covers the items listed on the checklist.
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GOOD
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GOOD
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TOO LITTLE
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TOO LITTLE
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Review: Provide an explanation for the following observations using principles of atomic structure. 1. There is an extremely large increase between the 2nd and 3rd ionization energies of Beryllium (1,757 kJ/mol up to 14,800 kJ/mol). Use an electron configuration to support your answer. b. Cl has a 1st IE of 1251 kJ/mol while Br has a 1st IE of 1140 kJ/mol
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Electron Affinity: What is electron affinity? Ionization energy in reverse … -IE is the energy required to remove an electron -EA is the energy released when an e- is acquired Atom + e- Values for EA will be negative since energy is released (exothermic) A more negative EA means a higher affinity for e-
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Electron Affinity: The Trend WHY? Relate it to ionization E!
Atoms that are hard to ionize (high IE) will also have a higher affinity for gaining electrons (very negative EA)
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Ionic Size: Cations are smaller than their atoms WHY?
After losing electrons, the atom now fills to a lower energy level, which is smaller Ionic Size: Cations are smaller than their atoms WHY? Li 152 pm Li + 78 pm Anions are larger. WHY? F -1 133 pm F 71 pm Adding electrons into the same orbital causes increased e- repulsions
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Ionic Size: The periodic trend is the same as that of atomic size
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Practice: a. Place in order of increasing atomic radius and justify your response. O C Si Si is larger than both O and C because it fills to the n=3 energy level, which is larger. C is larger than O because it has a lower nuclear charge, so it’s electrons are less attracted to the nucleus.
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Practice: b. Which has the largest ionization energy and why?
O has the highest IE Si will have the lowest since it’s outer electrons are in the n=3 shell and experience the most shielding. O is higher than C because it’s nuclear charge is greater, so the electrons are more strongly attracted to the nucleus and harder to remove.
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Practice: c. Which has the more negative electron affinity, O or C? Which atom will release more energy upon gaining an electron? Which atom has the greater “desire” to gain electrons? Oxygen
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Practice: d. Oxygen commonly forms the oxide ion, O-2. Predict and explain how the size will change as oxygen forms this ion. O-2 will be larger For O to turn into O-2, 2 electrons must be added. This increases electron repulsions and increases the radius.
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Practice: e. If you were comparing the successive ionization energies of a carbon atom (1st, 2nd, 3rd, etc), between which values would expect to see the largest increase and why? Carbon: 1s2 2s2 2p2 The first 4 electron removals will require less energy because they all come from the n=2 energy level and are somewhat shielded from the nucleus. The 5th IE will be much higher because it will come from n=1 and has almost no shielding from the nucleus.
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Practice: f. Which particle will have the larger radius: the oxide ion, O-2 or a neon atom, Ne Oxide ion: 1s2 2s2 2p6 Neon atom: 1s2 2s2 2p6 Both particles have same shielding and highest filled E level, only difference is nuclear charge. Neon’s is higher, so it is smaller.
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