Periodic Trends - Notes PDF

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Atomic Radius (size of neutral atom) 

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Periodic Trend: o Decreases from left to right across a period o Protons are added to the nucleus and electrons are added to the same principal energy level o As force of attraction between nuclei and electrons increases, the size of the atoms decreases. Group Trend: o Increases as you go down o Caused by more energy levels of electrons and therefore more electron shielding

Ionic Radius (size of charged ion) 

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Periodic Trend: o Decreases from left to right across a period o Cation radius decreases  As you go left to right, cations have more attraction (smaller size because more protons than electrons) o Anion radius decreases  The anions have a larger size than the cations, but also decrease left to right Group Trend: o Increases as you go down o Each row adds a new electron shell

First Ionization Energy (amount of energy needed to remove an outer electron from an atom and make it into an ion) 

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Periodic Trend: o Increases from left to right o More protons in the nucleus pulling in electrons, so it requires more energy to remove an outer electron o Outer electrons have more attraction to the nucleus Group Trend: o Decreases as you move down o More energy levels and more shielding o Outer electrons have less attraction to the nucleus

Effective Nuclear Charge (positive charge felt by the outermost/valence electrons) 

Periodic Trend: o Increases across a period

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o More protons with no accompanying increase in shielding Group Trend: o Decrease down a group o The number of protons increases but more shielding down a group...