1. Chemical Bonding How do atoms combine to form compounds? What holds them together?

2. Octet Rule States that atom tend to acquire the electron configuration of a rare gas How many valence electron are there in the rare gases? What is a full set of valence electron?

3. Lewis Electron dot Structure By Gilbert Lewis Consist of a chemical symbol of an element surrounded by a number of dots. The chemical symbol represents the nucleus of the atom. The dots represents the valence electrons Ex: 1A 2A 3A 4A 5A H..... Li.. Be.. B.. C.. N...

4. Types of bonds Ionic bonds Metallic bonds Covalent bonds

5. Bond A force that holds the atoms together

7. Metallic Bond Is the electrical attraction between the valence electron and the positive nuclei.

8. Properties Do not dissolve in water Conduct electricity Lustrous, malleable, ductile, and hard solids Made entirely of metals atoms Valence electrons are free to move throughout the substance, like a sea of electrons

9. Ionic Bonds Formed by the transfer of electrons from one atom to another to achieve stability Usually formed between Groups 1,2,3 and 6 or 7 Example : NaCl, MgCl 2 Na + Cl - ------> NaCl Mg 2+ Cl - ------> MgCl 2

12. Ionic Structure of Sodium Chloride Na+ and Cl- ions alternate each other

14. Properties of Ionic Compounds High melting and boiling point Compounds in the solid state are non conductors of electricity but in the molten or liquid state and in aqueous solution, are conductors of electricity

15. Brittleness Brittleness is a typical property of ionic compounds

16. Covalent Bonding Formed by the sharing of electrons between atoms Usually formed between H and elements in group 4,5,6,and 7 Are represented by dashes between atoms Single bond(-), double bond(=) and triple bond( )

17. Example: Show the covalent bond formation of H 2, O 2 and NH 3 H.. H  H-H........ : O.. O:  : O=O:......... N.. H  H.. N.. H  H-N-H. : H H

18. Types of Covalent Bonding Polar Covalent Nonpolar Covalent Bond

20. Polar Covalent Bond  formed when combining atoms differ in electronegativities Electronegativity  the ability of an atom to draw electrons toward itself Trend: Left to right increases top to bottom decreases Ex: H Cl + Ex: C O +

23. Nonpolar Covalent Bond Formed by equal sharing of electrons between nonmetallic atoms of the same kind resulting in zero differences in their electronegativities Ex: H 2, F 2

24. Predicting type of Bond using Electronegativity Difference Electronegativity Values of Some elements Li Be B C N O F 1.0 1.5 2.0 2.5 3.0 3.5 4.0 Na Mg Al Si P S Cl 0.9 1.2 1.5 1.8 2.1 2.5 3.0 K Ca Ga Ge As Se Br 0.8 1.0 1.6 1.8 2.0 2.4 2.8 Ex: Predict the type of bond form between the following elements a) etween the following pairs of element C and Cl  2.5 – 3 =.5 polar F and F  4 – 4 = 0 non polar Mg and O  1.2 - 3.0 = 1.8 ionic

25. Writing Lewis Structures for Covalent Compounds Steps Add up the total valence valence electron The atom with the highest covalency ( # of covalent bonds form by the atom) is considered as the central atom Bond the other atoms to the central atom by a single bond. Distribute the remaining valence electron to the attached atoms first then to the central atom last Check if the octet rule is followed by each atom If there is deficiency in the octet rule, form a multiple bond Ex: CO 2 total valence e = 4 + (6x2) = 16....C. O:... Covalency number = 4 2 :O=C=O:....

26. H LiBe NaMg KCa RbSr Cs Ba FrRa ACNO F AlSiPSCl GaGeAsSeBr InSnSbSeI TlPbBiPoAt He Ne Ar Kr Xe Rn