1. Unit 10: Chemical Bonding Section 1: Ionic and Covalent Bonding

2. Chemical Bonds Forces that hold atoms or ions together to make all molecules and compounds There are two main type of bonds – Ionic bonds and covalent bonds

3. Ionic Bonds Bonds achieved by transferring valence electrons – Due to a positive (metal) and negative (nonmetal) attraction

4. The Lewis Symbol In ionic bonding, atoms gain and lose electrons to achieve a noble gas electron configuration (a stable state) Lewis symbols use dots to represent an element’s number of valence electrons – Na has 1 valence electron  Na – Cl has 7 valence electrons  Cl – The order for applying dots is right, left, top, bottom, right, left, top, and bottom The maximum dots possible is 8, and the least dots possible is 1

5. Using the Lewis Symbol for Ionic Bonds sodium and chlorine  NaCl – Na Cl magnesium and chlorine  MgCl 2 – Mg Cl Cl The 1 st element needs to get rid of its valence electrons, and the 2 nd element needs to gain a total of eight valence electrons in order to be complete

6. Covalent Bonds Bonds achieved by sharing valence electrons – A bond between two nonmetals (two negatively charged atoms) There are two types of covalent bonds: nonpolar covalent and polar covalent – Nonpolar covalent bonds have equally shared valence electrons, where the attraction is even throughout – Polar covalent bonds have unequally shared valence electron, where the attraction is being pulled more toward the atom with the higher electronegativity

7. Determining Polarity If the electronegativity difference falls between 0.0 to 0.2, the bond is nonpolar covalent If the electronegativity difference falls between 0.3 to 1.4, the bond is polar covalent If the electronegativity difference is greater than 1.5, the bond is ionic

8. Determining Polarity Determine the polarity of MgCl 2 Mg = 1.2 and Cl = 3.0, so 3.0 – 1.2 = 1.8  IONIC

9. Using the Lewis Symbol for Covalent Bonds Lewis structure for SiH 4 H H H Si H  H Si H H H The goal is to get all the unpaired valence electrons to bond together