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الكيمـياء - Chemistry مواضيع الكيمياء العامة

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قديم 05-22-2007, 06:10 PM   #1
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افتراضي Bond and Molecular Polarity

Ionic Bonds


As a metal and a non-metal approach one another, the valence electrons interact and the metal (indicated by the red sphere) transfers its valence electrons to the non-metal (indicated by the blue sphere). The metal becomes positively charged (through the loss of electrons) and the non-metal becomes negatively charged (through the gain of electrons). In this way, both the metal and the non-metal complete their valence shell to obtain a stable electron configuration







An ionic bond is the chemical bond that results from the electrostatic attraction between positive ions (cations) and negative ions (anions) and a lattice structure results in which the cations are surrounded by anions and the anions are surrounded by cations



This type of bond is the most polar type of bond as indicated by the separation of charge




Covalent Bonds
As two non-metals approach one another, the valence electrons interact and a covalent bond is formed between the two non-metals which share a pair of electrons so that each obtains a filled valence shell






There are two types of covalent bonds. In a non-polar covalent bond the electrons are shared equally between the two atoms. (The nuclei and core electrons are indicated by the blue spheres and the bonding electrons are indicated by the lavender dots )




The electrons move around the nuclei with the electrons generating temporary positive and negative charges within the molecule




In a polar covalent bond the electrons are shared unequally between the two atoms. In this situation, one atom has a greater ability to pull the bonding electrons towards it and is said to be more electronegative. (The green sphere represents the more electronegative element.)






Again, the electrons move around the nuclei with the electrons spending the majority of the time near the more electronegative element. This generates a partial negative charge near the more electronegative element and a partial positive charge near the less electronegative element






Molecular polarity is dependent on bond polarity and the molecular geometry. For small molecules: If all the regions surrounding an atom are similar in their electronegativities, the molecule will be non-polar. If the regions are different, then the molecule will be polar

For large molecules there may be polar and non-polar regions



من مواضيع خالــد في المنتدى


التعديل الأخير تم بواسطة خالــد ; 05-22-2007 الساعة 06:24 PM
   
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