Lecture_2-1.pdf - eCoursePack Section 5.1 Tro Section...

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Types of Chemical Bonds ü Every other atom in the periodic table would like to attain a valence electron configuration like the noble gases, which means achieving the ns 2 np 6 configuration (or 1 s 2 configuration). ü Based on their ability to lose, gain, or share electrons, the elements in the periodic table can be divided into three types: 1. Electropositive Elements—The atoms of these elements are the metals. They have relatively low ionization energies and the tendency to lose electrons to achieve a filled outer shell. Thus, they readily lose electrons to form cations. 2. Electronegative Elements—The atoms of these elements are the nonmetals (excluding the noble gases). They have relatively high exothermic electron affinities and the tendency to acquire electrons to achieve a filled outer shell. Thus, they readily gain electrons to form anions. 3. Noble gases—The atoms of these elements are set apart from all the other elements in the periodic table. They have ionization energies and electron affinities that are endothermic and large, and have little tendency to lose or gain electrons. eCoursePack Section 5.1 Tro Section 5.2 (1 st ed)/4.2 (2 nd ed)
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Types of Chemical Bonds ü As a general rule, elements become less metallic and more nonmetallic across a period in the table and more metallic and less nonmetallic down a group. A solid step line marks the dividing line between elements that are predominantly metallic from elements that are predominantly nonmetallic. Elements that have properties that are intermediate between metals and nonmetals are called metalloids or semimetals . eCoursePack Section 5.1 Tro Section 5.2 (1 st ed)/4.2 (2 nd ed)
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Types of Chemical Bonds ü Three different types of chemical bonds can form depending on the three possible combinations of the electropositive or electronegative nature of the atoms involved in the bonding. These are: eCoursePack Section 5.1 Tro Section 5.2 (1 st ed)/4.2 (2 nd ed)
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Ionic Bond ü For example, common table salt is sodium chloride. When sodium (Na) atoms and chlorine (Cl) atoms combine in sodium chloride, each sodium atom loses an electron, forming a Na + cation, and each chlorine atom gains an electron forming a Cl anion. ü The oppositely charged ions are then attracted to each other in a 1:1 ratio to form the sodium chloride in the solid state. ü Consequently, the ionic bonding in sodium chloride is formed only when a large number of Na + cations and Cl anions are packed together as a solid, and collectively held by the electrostatic attractions between the ions.
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