Use details of the modern atomic theory and periodicity toexplain why a. atomic
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Question
Use details of the modern atomic theory and periodicity toexplain why a. atomic radii becomes larger as the atomic number within afamily gets larger. b. atomic radii becomes smaller as the atomic number within aperiod gets larger. c. the radius of an oxide ion is larger than the radius of aoxygen atom. d. the first ionization energy of aluminum is smaller than thefirst ionization energy of magnesium. e. the third ionization energy of an element is always largerthan its second ionization energy. Use details of the modern atomic theory and periodicity toexplain why a. atomic radii becomes larger as the atomic number within afamily gets larger. b. atomic radii becomes smaller as the atomic number within aperiod gets larger. c. the radius of an oxide ion is larger than the radius of aoxygen atom. d. the first ionization energy of aluminum is smaller than thefirst ionization energy of magnesium. e. the third ionization energy of an element is always largerthan its second ionization energy.Explanation / Answer
a. As you go down a family (down a column), you are adding acompletely filled valence shell of electrons. The electrons alreadypresent on the atom will help shield these new electrons from thepositive nucleus, so the electrons can travel further away from thenucleus. This will increase the radius of the atom. b. As you travel across a period, you are adding a single electron.You are also adding a proton. Shielding isn't extensive, so thiselectron gets pulled closer in to the nucleus. This decreases theradius. c. An oxide ion has two extra electrons added to it. You are notadding protons, so these electrons do not get drawn in to thenucleus, and the electrons can effectively spread out. Thisincreases the size. d. The electron orbitals go like this: 1s2,2s2,2p6,3s2,3p6...Magnesium has a completed shell (3s2). It is very difficult to pullan electron from an atom with a completed shell, because all atomsstrive for completed shells. Aluminum has a random unpairedelectron floating around, and this is easier to grab. Thus theionization energy is lower. e. By the time you've pulled two electrons away from the nucleus,the atom is very positively charged. Trying to pull yet anotherelectron away from the very positive nucleus becomes even moredifficult, because the nucleus is pulling very hard on theelectrons now. This will increase the ionization energy.
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