Molecular and Ionic Compound Structure and Properties

2.1 Types of Chemical Bonds

Essential Knowledge:

*These are taken directly from College Board

• Electronegativity values for the representative elements increase going from left to right across a period and decrease going down a group. These trends can be understood qualitatively through the electronic structure of the atoms, the shell model, and Coulomb’s law.  (SPQ-1.A.1)  

• Valence electrons shared between atoms of similar electronegativity constitute a nonpolar covalent bond. For example, bonds between carbon and hydrogen are effectively nonpolar even though carbon is slightly more electronegative than hydrogen.(SPQ-1.A.1)  

• Valence electrons shared between atoms of unequal electronegativity constitute a polar covalent bond. 

a) The atom with the higher electronegativity will develop a partial negative charge relative to the other atom in the bond. 

b) In single bonds, greater differences in electronegativity lead to greater bond dipoles. 

c) All polar bonds have some ionic character, and the difference between ionic and covalent bonding is not distinct but rather a continuum. (SAP-3.A.3) 

• The difference in electronegativity is not the only factor in determining if a bond should be designated as ionic or covalent. Generally, bonds between a metal and nonmetal are ionic, and bonds between two nonmetals are covalent. Examination of the properties of a compound is the best way to characterize the type of bonding.  (SAP-3.A.4) 

In a metallic solid, the valence electrons from the metal atoms are considered to be delocalized and not associated with any individual atom.  (SAP-3.A.5)