2. CHEMICAL BONDING CHRISTENE JOY T. BALILI

3. OBJECTIVES  Understand how atoms combine  Relate the type of bond formed between two or three elements to their location in the periodic table.  Use atomic electron configurations and the octet rule to draw Lewis structures for molecules.  Write the formula of ionic and covalent bond.

4. CHEMICAL BONDING -force of attraction that holds two atoms together.

5. WHAT IS CHEMICAL BONDING? Chemical Bonding refers to the formation of a chemical bond between two or more atoms, molecules, or ions to give rise to a chemical compound. These chemical bonds are what keep the atoms together in the resulting compound.

7. METALLOIDS

10. VALENCE ELECTRONS – THE ELECTRONS IN THE OUTERMOST ENERGY LEVEL OF AN ATOM

11. VALENCE ELECTRO N These are electrons that can participate in the formation of a chemical bond. The presence of valence electrons can determine the element's chemical properties and whether it may bond with other elements. Determining the Number of Valence Electrons

12. HOW MANY VALENCE ELECTRONS? Hydrogen 1 Valence Electron Lead 4 Valence Electrons Xenon 8 Valence Electrons Sulfur 6 Valence Electrons

17. Electron Dot Diagram

19. What Could the Oxidation Number be? +1 or -1 because it can gain or lose one electron -2 because it will gain two electrons 0 because it will not gain or lose electrons +2 because it will lose two electrons

21. ELECTRONEGATIVITY Electronegativity – the relative ability of an atom in a molecule to attract shared electrons to itself. Increases from left to right across a period Decreases down a group of representative elements Non-metals tend to have high electronegativities, so they gain electrons readily.

22. Types of Chemical Bonds Ionic Covalent Metallic

23. Ionic compound results when a metal reacts with a nonmetal.

24. Write the Lewis Symbol of the selected elements. Take note of the electronegativity value of both elements. Subtract the electronegativity value of the metallic element from the nonmetallic element.. ․ Na٠ EN =0.90:Cl:Cl EN=3.0 ֗ Thus: 2.0 -0.90=2.1 *If the difference is greater than 1.9, complete transfer of electron/s is possible.

25. INDICATE THE FORMATION OF CATION AND ANION. NA + CL - Positive ions are called cations. Negative ions are called anions. Most ionic compounds are formed by chemical combinations of GROUP IA or IIA elements with GROUP VI A or VII elements.

26. Electron transfer of potassium atom and an iodine atom.

27. STABLE ELECTRON CONFIGURATIONS AND CHARGES ON IONS Atoms in stable compounds usually have a noble gas electron configuration.  Metals lose electrons to reach noble gas configuration.  Nonmetals gain electrons to reach noble gas configuration.

29. STABLE ELECTRON CONFIGURATIONS AND CHARGES ON IONS Predicting Formulas of Ionic compounds Chemical compounds are always electrically neutral.

30. WRITING IONIC COMPOUNDS Write the symbol for the positive ion first. Write the symbol for the negative ion next. Assign subscripts to make the compound neutral.

31. 1.Write the chemical formula for the ionic compound formed by each pair of ions. Mg 2+ and I − Na + and O 2− Answer MgI 2 Na 2 O Exercises

32. IONIC COMPOUNDS CONTAINING POLYATOMIC IONS Polyatomic ions are ions that are composed of two or more atoms that are linked by covalent bonds, but that still have a net deficiency or surplus of electrons, resulting in an overall charge on the group. A metal plus a polyatomic ion yields an ionic compound.

33. Metals combine with polyatomic ions to give ionic compounds.

34. Ionic Bonding Occur between metals (+) and non-metals (-) Involve a transfer of electrons from the metal and the non metal. Two elements have electronegative difference of 1.9 or greater

36. A bond formed by the sharing of electrons Between nonmetallic elements of similar electronegativity. Formed by sharing electron pairs Stable non-ionizing particles, they are not conductors at any state Examples; O 2, CO 2, C 2 H 6, H 2 O, SiC

38. When carbon is one of your atoms, it will always be in the center Sometimes you only have two atoms, so there is no central atom Cl2 HBr H2 O 2 N2 HCl

39. RULES IN FORMING COVALENT BONDS A. Get the total available valence electrons in a compound. For CO 2 Carbon atom has 4 valence electrons Oxygen atom has 6 valence electrons Total Available Valence Electrons (TAVE) = (1 C atom x 4)+ (2 O atoms x 6) = 4 + 12 =16 B. Compute for the OCTET RULE requirement that each atom should have 8 valence electrons to become stable. Number of electrons based on OCTET RULE = (1 C atom x 8) + (2 O atoms x 8) = 8 + 16 =24

40. C. Subtract B from A, then divide the difference by 2 because a pair of a shared electron is equal to 1 bond. The quotient will give you the number of bonds around the central atom. Number of bonds = (24 -6) 2 = 4 Thus, there will be 4 bonds surrounding carbon atoms as shown in the Lewis structure.

41. D. Use the remaining available electrons to fill the valence shell for each atom Number of electrons remaining =Total Available Electrons – Number of bonds (2) =16-4(2) =16-8 =8 or

42. H2H2 A.Total Available Valence Electrons (TAVE) = 2 H atom x 1 = 2 B. Number of electrons based on OCTET RULE =2 H atom x 2 = 4 C. Number of bonds = B-A 2 =4 - 2= 2 ÷ 2 = 1 bond D. Remaining = 2 – 1(2) = 0

43. CH 4 Carbon atom has 4 valence electrons Hydrogen atom has 1 valence electrons A.Total Available Valence Electrons (TAVE) = 1 C atom x 4 + 4 H atom x1 =4+4 =8 B. Number of electrons based on OCTET RULE = (1 C atom X 8)+ (4 H atom X 2) = 8 + 8 =16 C. Number of bonds = B-A 2 = 16 – 8 2 = 4 bonds D. Remaining = 8-4(2) = 0

44. Bonds in all the polyatomic ions and diatomics are all covalent bonds.

45. NONPOLAR COVALENT BONDS when electrons are shared equally If the electronegativity difference is equal to 0.4 or less it results to a non polar covalent bond. H 2 or Cl 2

46. POLAR COVALENT BONDS when electrons are shared but shared unequally If the electronegativity is less than 1.9 and more than 0.4. H2OH2O

47. NONPOLAR MOLECULES Molecule is Equal on all sides Symmetrical shape of molecule (atoms surrounding central atom are the same on all sides) 46 H H HHC Draw Lewis dot first and see if equal on all sides

48. HCl -- ++ Polar Molecule Unequal Sharing of Electrons 47

49. Cl Non-Polar Molecule Cl Equal Sharing of Electrons 48

50. HCl Polar Molecule Not symmetrical H B 49

51. H H Non-Polar Molecule Symmetrical H B 50

52. HH O WATER IS A POLAR MOLECULE ANY TIME THERE ARE UNSHARED PAIRS OF ELECTRONS ON THE CENTRAL ATOM, THE MOLECULE IS POLAR 51

53. METALLIC BOND Metallic bonding is the type of bonding found in metallic elements. This is the electrostatic force of attraction between positively charged ions and delocalized outer electrons. Metallic bonding refers to the interaction between the delocalized electrons and the metal nuclei.

54. DELOCALISED ELECTRONS When metal atoms bond with one another, their outer shell electron orbitals merge. The electrons are no longer confined to one particular atom and are free to move within the merged orbitals, which form a region that stretches throughout the whole metal. We say that these electrons are delocalised and that they form a sea of delocalisation.

55. ELECTROSTATIC ATTRACTION The metal atoms form ions with a positive charge, since they are now no longer associated with their outer shell electrons. Positively charged ions are known as cations.