Module 4: Part A: Bond Recognition

Read the short discussion in Corwin’s sections 12.1-12.3 on pages 310-317 on the difference between Ionic and covalent bonding.

There are three types of chemical bonds:
 Ionic, Covalent, and Metallic

There is a simpler way to predict if two atoms will transfer their electrons or share their electron in pairs making a compound. Skip back to page 325. Read about the Pauling’s Scale of Electronegativities. Figure 12.9 shows the electronnegativity of each element on the periodic chart. This table will be needed in Module Four Part II Bond Polarity.

 If the difference in electronegativity between two atoms is greater than 1.7, the electrons will transfer from one atom to the other to make ions and Ionic Compounds. Ionic (sometimes called Electrovalent) Compounds are also called salts and in nature they are called minerals. We will over simplify this concept to say if a metal meets a nonmetal ionic bonds are formed (if a table of electronegativity is not included).

 If the difference between the electronegativites of two atoms is less than 1.7 then the two atoms will share electrons in pairs. Two types of sharing bonds are formed. Metallic and Covalent.

 Metallic Bonds are formed when two metals share electrons such as alloys of metals. 24 karat gold is pure gold and is very soft. But Jewelry is usually 10-18 Karat Gold, meaning that another metal is mixed with gold to make the solid harder. We will not study Metallic Bonds in this course, but you should know that two metals share electrons in pairs to make Metallic Bonds.

 Covalent Bonds are formed when two nonmetals bond together. The elements carbon, oxygen, hydrogen, sulfur, nitrogen, phosphorus, chlorine, and bromine will be the main nonmetals studied in drawing dot structures of molecules. Bonds between these nonmetals are always Covalent.

Part A of Module Four should now be easy. Predict what type of bond will be made if two atoms combine:

In General:

Metal-Metal = Metallic Bond  (example: Ag(5)-Au(14)-Cu(5) = 14 Karat Gold)

Metal-Nonmetal = Ionic Bond (example: Na-Cl)

Nonmetal-nonmetal = Covalent Bond (example: H2O)