Types of Chemical Bonds Chapter 12.1

Introduction A bond is the force that holds a group of two or more atoms together. We will study three main types of bonding.

Ionic Bonding (No Sharing) This type of bond takes place between a metal and a nonmetal. A nonmetal actually takes e- away from a metal, causing each atom to become charged. Ionic bonds are stable solids that dissolve in water.

Covalent Bonding (Complete Sharing) This bonding takes place between nonmetals only. The atoms involved in this type of bonding actually share each others electrons.

Polar Covalent Bonding (Uneven Sharing) This type of bonding is also between nonmetals. The main difference between this and covalent bonding is that the sharing is not equal. One of the atoms will have more of the e- than the other. The atoms with more of the e- around it is said to be more electronegative.

Electronegativity, Bond Polarity, and Stable E- Configurations Chapter 12.2, 12.3, and 12.4

Electronegativity (1) This is the ability of an atom to attract electrons to itself. In general, electronegativity increases as you go up and to the right on the periodic table. For exact values you must look at a table like the one shown on page 362.

Electronegativity (2) By finding the difference in electronegativity between the atoms in a compound, you can determine which of the three types of bonding is taking place. Use the following table to determine bonding type: Covalent: 0 Polar Covalent: 0.1 – 1.7 Ionic: 1.8 - above

Electronegativity (3) Determine the type of bonding involved in the following compounds: O – H H – H H – F

Bond Polarity and Dipole Moments (1) All compounds other than covalent ones, are said to have a dipole moment, meaning they have a negative and positive end. Any compound with a dipole moment is said to be polar. Dipole moments can be represented pictorially by drawing an arrow starting at the atom with the lowest electronegativity and pointing towards the one with the highest.

Bond Polarity and Dipole Moments (2) Draw an arrow showing the dipole moment for the following: H – I Na – Cl O – C

Stable Electron Configurations and Charges on Ions (1) All of the atoms in the periodic table want very badly to have full orbitals and be like one of the noble gases. They can achieve this by giving or taking e-. This is easily seen by looking at e- configurations.

Stable Electron Configurations and Charges on Ions (2) Look at the e- config for O: 1s2 2s2 2p4 Would it be easier to lose 6 e- or gain 2? Gain 2 to become O2- and be 1s2 2s2 2p6 Look at the e- config for Na: 1s2 2s2 2p6 3s1 Would it be easier to lose 1 e- or gain 7? Lose 1 to become Na+ and be 1s2 2s2 2p6 In both cases the Na and O look like Ne on the atomic level.