1. Chapter 22 Section 2 Pages 694-702
Chemical bonding
Chapter 22 Section 2
Pages

2. Chemical Bonding Bonding – attractions between atoms or ions
There are several types of chemical bonds, but we will discuss three of the strongest types
1. Covalent bonds
2. Metallic bonds
3. Ionic bonds

3. Covalent Bonds
Covalent bonds – bonds formed from atoms sharing pairs of electrons
 Molecules formed this way: sugar, water
- NO charged particles / ions involved
- Sharing electrons between atoms
 Each atom “donates” one electron to the shared pair

4. Covalent Bonds - Two atoms can share up to 3 pairs of electrons
 1 shared pair = single covalent bond
 2 shared pairs = double covalent bond
 3 shared pairs = triple covalent bond

5. Covalent Bonds
- Each shared pair represented as a line in a structural formula
 Example: H - H
*this is a single covalent bond
**Goal of bonding is to fill the outer energy level and become stable

6. Covalent Bonds – Electron dot diagrams
Valence electrons – electrons in the
outermost energy levels of an atom
Electron dot diagrams show the valence
electrons as dots surrounding the
chemical symbol
 The chemical symbol represents the
nucleus and all inner level electrons
Electron dot diagrams show only the electrons in the outer energy level of an atom.

7. Covalent Bonds – Electron dot diagrams
Each hydrogen shares one pair of electrons with the oxygen atom

8. Metallic bonds 2. Metallic bond – Closely packed metal atoms
- Outer energy levels of metal atoms overlap
- Valence electrons can move and flow freely
throughout the substance
- Allows flexibility of material to bend
- Allows easy flow of electricity through material

9. Ionic Bonds
3. Ionic bond – bond between oppositely charged ions, involving a total transfer of electrons between atoms
- Ion – a charged particle
- Cations (which lose electrons and become positively charged) bond to Anions (which gain electrons and become negatively charged)

10. Ionic Bonds
- One atom gains an electron(s) and one atom loses an electron(s)
- The now oppositely charged ions are attracted to each other due to magnetism
 Opposite charges attract

11. Ionic Bonds
Ionic bonds usually are formed by bonding between metals and nonmetals.

12. Ionic Bonds
One cation can bond to multiple (more than one) anion

13. Ionic Bonds
When atoms form an ionic compound, their electrons are shifted to the other atoms, but the overall number of protons and electrons of the combined atoms remains equal and unchanged. Therefore, the compound is neutral.

14. Ionic Bonds
- Ionic compounds are networks but there is a basic ratio of cations to anions
 Formula unit – the basic ratio of ions
Example: NaCl  1 Na : 1 Cl