1. Bonding

2. Why bonding???? Nature prefers stability Atoms that exist alone are unstable Atoms bond with other atoms to become more stable This is why we rarely find lone atoms in nature Diatomics – H 2, N 2, O 2, F 2, Cl 2, Br 2, I 2 They will bind with other atoms to form molecules Share or transfer valence electrons

3. Why bonding???? Binding causes valence electrons to redistribute This makes the atoms more stable, which is preferred STABILITY!!!! Drives bonding

4. What is a bond??? The mutual attraction between valence electrons of one atom and nuclei of another atom

5. Types of bonds The arrangement of electrons determines the type of bond 3 types Ionic Covalent metallic

6. Ionic bonding Electrical attraction between cation and anion and transfer of an electron Between a metal and nonmetal One form L and one from R side of PT Metal donates e - to nonmetal Form clusters of alternating charge

7. Covalent Bonding Two non metals SHARE a pair of electrons Both will obtain an octet Electrons will be shared equally between the two atoms

8. Covalent Bonding Metallic Special type of covalent bond Between two or more metal atoms Electrons become ‘delocalized’ ‘sea of electrons’

9. Covalent Bonding Metallic Strength depends on nuclear charge and number of electrons shared More electrons that are shared, stronger the bond NC hard to measure Can use heat of vaporization – amount of energy required to turn metal into a gas

10. Determining Bond Types Bonds in nature are never purely covalent or ionic – somewhere in the middle Non-polar covalent Polar covalent Ionic Can determine by looking at electronegativity

11. Determining Bond Types Electronegativity – measure of an atom’s ability to steal electrons The difference in electronegativites will tell us which bond type exists between the atoms

12. Non-Polar Covalent Δ EN is 0.0 – 0.3, 0 – 5% ionic character The shared electrons and charge is evenly distributed between bonded atoms

13. Polar-Covalent Δ EN 0.3 – 1.67, 5-50% ionic character “Polar” – one of the atoms has greater ownership of the shared pair of electrons Unequal sharing of e - Unequal share of e - produces a dipole Compound has areas of partial (+) and partial (-) charge Partial is indicated by δ + or δ -

14. Polar Covalent Water!!

15. Ionic Δ EN 1.67- 4.0, 50 – 100% ionic character Valence electrons from one atom are transferred to another atom Two ions are formed (cation and anion) Attract one another

16. Let’s Practice Use electronegativity differences to classify bonding between chlorine, Cl (EN = 3.0), and the following elements Calcium, Ca (EN = 1.0) Oxygen, O (EN = 3.5) Bromine, Br (EN = 2.8) Indicate which atom is more negative