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  Lewis' Theory of Chemical Bonding Valence Electrons An atom consists of a positively charged nucleus and some negatively charged electrons. These particles interact with each other at all times by means of electrical forces, also known as electrostatic or Coulombic forces. Electrostatic forces can attract particles together or drive them apart. Oppositely charged particles, like a nucleus (+) and an electron (-), are attracted to one another. Similarly charged particles, like a pair of electrons, repel each other. Lewis postulated (and it was later confirmed) that an atom's electrons could be divided into two groups: core and valence. The core electrons stay very close to the nucleus and constantly feel its strong attraction. These electrons are unaffected by neighboring atoms. Valence electrons, on the other hand, stay farther away from the nucleus and experience much less electrostatic attraction. As a result, these electrons are readily influenced by neighboring atoms.
Review problems Test your understanding of this material by filling in the blanks in the following paragraph. Write your answers on a piece of paper and then click "answers" to see the complete paragraph. If you have trouble with this material, try writing the same kind of paragraph about the carbon atom (atomic number 6, mass 12). The oxygen atom. The oxygen atom has an atomic number of 8 and an atomic mass of 16. From this information, you know that the oxygen nucleus contains ____ protons, ____ neutrons, and ____ electrons. The oxygen nucleus carries an electrical charge of ____. An oxygen atom also contains ____ electrons. Each electron carries an electrical charge of ____. The nucleus and the electrons ____ (attract/repel) each other, while pairs of electrons ____ (attract/repel) each other. The ____ can be divided into two groups: ____ and ____. The ____ electrons, of which there are ____, stay very close to the nucleus. The ____ electrons, of which there are ____, are much farther away from the nucleus and participate in chemical bonding. |
