13Periodicity07

13Periodicity07 - Sizes of Atoms and Ions Periodicity Sizes...

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CHEM13 Periodicity Sizes of atoms and ions Ionization Energy Electron affinity Electronegativity Metallic Character CHEM13 Atomic radii increase with increasing electron shielding . Atomic radii decrease with increasing effective nuclear charge . Cations have smaller radii than their neutral atoms. Anions have larger radii than their neutral atoms. Sizes of Atoms and Ions
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CHEM13 SIZES OF ATOMS AND IONS CHEM13 Ionization energy (IE) is the energy necessary to remove an electron from an atom, molecule or ion. Na( g ) ! Na + ( g) + e - Ionization energy is always endothermic. IONIZATION ENERGY Moving down a group, IE decreases because of increased electron shielding . Moving across a row from left to right, IE increases because of increased effective nuclear charge . It is easier to remove an electron from a 2p orbital than it is to remove one from a 2s orbital. It is easier to remove an electron if it is un-paired than if it is paired.
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CHEM13 ELECTRON AFFINITY Electron affinity is the opposite of ionization energy. Electron affinity is the energy change when a gaseous atom gains an electron to form a gaseous ion: Cl( g ) + e - ! Cl - ( g ) Electron affinity can either be exothermic (as the above example) or endothermic: Na( g ) + e - ! Na - ( g ) Electron affinity generally increases in magnitude toward the top and the right on the periodic table. CHEM13
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13Periodicity07 - Sizes of Atoms and Ions Periodicity Sizes...

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