1.0 Handouts (Chapter 1)(1)

1.0 Handouts (Chapter 1)(1) - How to predict the number of...

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How to predict the number of valence electrons for an atom Introduction: The valence electrons are the ones in the outer most shell of an atom. This number is important for determining the number of bonds an atom will form, the number of unpaired electrons and its formal charge. How to: The number of valence electrons in a neutral atom is equal to its main group number. This can be found by which column it is on the periodic table. 1 2 3 4 5 6 7 8 . . . . . . . . . . . . . . . . . . . . H He Li Be B C N O F Ne Na Mg Al Si P S Cl Ar K Ca Ga Ge As Se Br Kr Rb Sr In Sn Sb Te I Xe . . . . . . . . . . . . . . . . . . Transitions Metals (main group numbers) Examples Hydrogen (H) has 1 valence electron. Carbon (C) has 4 valence electrons. Sulfur (S) has 6 valence electrons. Potassium (K) has 1 valence electron. Advanced: If an atom or molecule has an overall charge, then one of more of its atoms has an imbalance in its number of valence electrons. For example, Ca +2 has zero valence electrons because Ca normally has 2 valence electrons but with a 2+ charge it is missing two electrons.* F -1 has 8 valence electrons. S -2 has 8 valence electrons. * We could also say that Ca 2+ has 8 valence electrons because if it looses all the electrons in its outer valance shell then the next lower shell becomes the outer valence shell. K. Shimizu
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How to predict the relative electronegativity (EN) of an atom Introduction: Electronegativity is a measure of the attraction of an atom for an electron. The higher the electronegativity the greater the attraction of that atom for an electron. The electronegativity scale goes from 0 to 4.0 (for Fuorine). How to: ±luorine is the most electronegative atom (EN = 4.0). Therefore atoms closer to Fuorine will be more electronegative. The trend is for elecronegativity to increase going across and up the periodic table. . . . . . . . . . . . . . . . . . . . . H He Li Be B C N O ± Ne Na Mg Al Si P S Cl Ar K Ca Ga Ge As Se Br Kr Rb Sr In Sn Sb Te I Xe . . . . . . . . . . . . . . . . . . Transition Metals Examples: Oxygen is more electronegative (likes electrons more) than carbon. Chlorine is more electronegative than iodine. Sulfur is more electronegative than silicon. for predicting EN, should be here H Advanced: A key exception to the above trends is hydrogen. Although we often put hydrogen all the way on the left hand side of the periodic table with the alkali earth metals such as Li and Na, the EN of hydrogen is much closer to the third column elements like boron. This means that C-H bonds are only weakly polarized because they have very similar electronegativities, with carbon being slightly more EN than hydrogen. EN increases going across periodic table K. Shimizu
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How to predict ionic and covalent bonds. Introduction:
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1.0 Handouts (Chapter 1)(1) - How to predict the number of...

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