7a Both Na and Cs are alkali metals with one valence electron Na is in n 3 while Cs is in n 6 Since Na has fewer completed shells than Cs it experiences less electron to electron repulsion causing its atomic radius to be smaller 7b Both Ca and Br are in n 4 so they experience the same relative shielding Ca has 20 protons while Br has 35 Since Ca has fewer protons than Br it experiences less effective nuclear charge causing its atomic radius to be larger 7c K and Cl are both isoelectronic to Ar so they experience the same electron repulsion K has 19 protons while Cl has 17 Since K has more protons than Cl it exerts a greater effective nuclear charged resulting in a smaller ionic radius 8a Both Be and Ba are alkaline earth metals with two valence electrons Be is in n 2 while Ba is in n 6 Since Be has fewer completed shells than Ba its effective nuclear charge is much more significant This stronger attraction to the nucleus increases the energy required to remove an electron 8b Both I and Sr are in n 5 I has 53 protons while Sr only has 38 Since I has more protons its effective nuclear charge is greater resulting in a greater amount of energy to remove an electron 8c Both N and O are in n 2 N has 3 electrons in its P orbital causing it to be half filled while O has 4 electrons in its P orbital causing it to be partially filled It requires more energy to remove an electron from a half filled orbital than it does to remove an electron from a partially filled orbital 8d An atom s second ionization energy will always be greater than its first because after the first electron is removed the electron to electron repulsion is reduced causing the effective nuclear charge to become more significant This increase in attraction causes an increase in the amount of energy required to remove an additional electron 9a Both N and F are in n 2 N has 3 electrons in its P orbital while F has 5 Giving an electron to N would cause it to have a partially filled P orbital and a higher energy Giving an electron to F would fill its P orbital and cause it to become more stable For this reason the electron affinity of N is less than that of F 9b Electron affinity can be described as an atom s likelihood of gaining an electron Sine Zn has a full S orbital and a full D orbital the likelihood of it gaining an electron is 0 It is not favorable for the atom to gain an electron 10a The electronegativity of O is greater than that of N because O is closer to F
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