Chemical Bonding - General Chemistry 1 SHS

Presents how atoms make bonds with other atoms to become stable

1. OCTET RULE GENERAL CHEMISTRY 1

2. OCTET RULE Atoms tend to gain, lose, or share electrons until they are surrounded by eight valence electrons .

3. DUPLET RULE Some elements can be stable with two electrons in their shell.

4. CHEMICAL BOND It is the force of attraction that exists between the atoms. It can be formed by transferring or sharing of electrons.

5. IONS An electrically charged atom formed by the loss or gain of one or more electrons

6. CATION (+) METALS 1-3 ve

7. ANION (-) NONMETALS 5-7 ve

8. Atom EC Outermost EL Ve - Dot Symbol Net charge Lithium Boron Magnesium Chlorine Neon Identifying Net Charges

9. Atom EC Outermost EL Ve - Dot Symbol Net charge Sulfur Silicon Tin Barium Indium Identifying Net Charges

10. IONIC COMPOUNDS GENERAL CHEMISTRY 1

11. IONIC COMPOUND It is a compound formed by ions bonding together through electrostatic forces . It is formed through a give and take relationship between a metal and a nonmetal. An example of an ionic compound is table salt or sodium chloride ( NaCl ) which is formed from a sodium ion and chloride ion.

12. IONIC COMPOUND

13. IONIC COMPOUND In nature, the ordered arrangement of ionic solids gives rise to beautiful crystals. (A) Amethyst - a form of quartz, SiO 2 , whose purple color comes from iron ions. (B) Cinnabar - the primary ore of mercury is mercury (II) sulfide, HgS . (C) Azurite - a copper mineral, Cu 3 (CO 3 ) 2 (OH) 2 . (D) Vanadinite - the primary ore of vanadium, Pb 3 (VO 4 ) 3 Cl.

14. PROPERTIES OF IONIC COMPOUND Ionic compounds have high melting points .

15. PROPERTIES OF IONIC COMPOUND Ionic compounds are generally hard, but  brittle.

16. PROPERTIES OF IONIC COMPOUND Another characteristic property of ionic compounds is their  electrical conductivity .

17. REPRESENTING IONIC COMPOUND LEWIS DOT SYMBOL CHEMICAL NAME CHEMICAL FORMULA

18. Cl SODIUM AND CHLORINE LEWIS DOT SYMBOL Na + Na + Cl + - CHEMICAL FORMULA Na Cl + - NaCl CHEMICAL NAME Sodium + Chlorine = Sodium Chloride

19.   Fl Fl Fl MAGNESIUM AND FLUORINE LEWIS DOT SYMBOL Mg + Mg + 2+ - CHEMICAL FORMULA Mg Fl 2+ - MgFl 2 CHEMICAL NAME Magnesium + Fluorine = Magnesium Fluoride 2

20.   Al O   O ALUMINUM AND OXYGEN LEWIS DOT SYMBOL + Al + 3 + 2- 3 O O Al 2

21. ALUMINUM AND OXYGEN CHEMICAL FORMULA Al 2 O 3 CHEMICAL NAME Aluminum + Oxygen = Aluminum Oxide O Al 3 + 2-

22. COVALENT COMPOUNDS GENERAL CHEMISTRY 1

23. COVALENT COMPOUND Elements having very high ionization energies are incapable of transferring electrons, and elements having very low electron affinity cannot take up electrons.

24. COVALENT COMPOUND A covalent bond is formed by the equal sharing of electrons from both participating atoms. The pair of electrons participating in this type of bonding is called a shared pair or bonding pair .

25. COVALENT COMPOUND Covalent bonds are also called molecular bonds . Sharing of bonding pairs will ensure that the atoms achieve stability in their outer shell , which is similar to the atoms of noble gases.

26. COVALENT COMPOUND Covalent bonding can be achieved in two ways: Sharing of electrons between atoms of the same kind, for example, formation of H2, Cl2, O2, etc. Sharing of electrons between atoms of different kinds, for example, formation of CH4, H2O, NH3, etc.

27. COVALENT COMPOUND How about Carbon?

28. PROPERTIES OF COVALENT COMPOUND Covalent bonding does not result in the formation of new electrons. The bond only pairs them. They are very powerful chemical bonds that exist between atoms. A covalent bond normally contains an energy of about ~80 kilocalories per mole (kcal/ mol ).

29. PROPERTIES OF COVALENT COMPOUND Covalent bonds rarely break spontaneously after it is formed. Covalent bonds are directional, where the atoms that are bonded showcase specific orientations relative to one another. Most compounds having covalent bonds exhibit relatively low melting points and boiling points.

30. PROPERTIES OF COVALENT COMPOUND Compounds with covalent bonds usually have lower enthalpies of vaporization and fusion. Compounds formed by covalent bonding don’t conduct electricity due to the lack of free electrons. Covalent compounds are not soluble in water.

31. LDS FOR COVALENT COMPOUNDS Electron dot structures of covalent molecules are written with respect to the octet rule. According to this rule, all the atoms in the molecule will have eight electrons in their valence shell except the hydrogen atom. Hydrogen will have only two electrons because only two electrons complete its first shell to attain helium configuration.

32. LDS FOR COVALENT COMPOUNDS For Example, the oxygen atom, which has six electrons in its valence shell, completes its octet by sharing its two electrons with two hydrogen atoms to form a water molecule .

33. LDS FOR COVALENT COMPOUNDS SINGLE COVALENT BOND

34. LDS FOR COVALENT COMPOUNDS DOUBLE COVALENT BOND

35. LDS FOR COVALENT COMPOUNDS DOUBLE COVALENT BOND

36. LDS FOR COVALENT COMPOUNDS DOUBLE COVALENT BOND

37. LDS FOR COVALENT COMPOUNDS TRIPLE COVALENT BOND

38. LDS FOR COVALENT COMPOUNDS FOR POLYATOMIC IONS Recall that a polyatomic ion is a group of atoms that are covalently bonded together and which carry an overall electrical charge. The ammonium ion, is formed when a hydrogen ion (H +) attaches to the lone pair of an ammonia (NH3 ) molecule in a coordinate covalent bond.

39. LDS FOR COVALENT COMPOUNDS EXERCISE Write Lewis electron structures for the following molecules: SCl2 HCN CH2O

40. EXCEPTIONS TO THE OCTET RULE ODD ELECTRON MOLECULE

41. EXCEPTIONS TO THE OCTET RULE ELECTRON-DEFICIENT MOLECULE

42. EXCEPTIONS TO THE OCTET RULE EXPANDED VALENCE SHELL MOLECULE

43. EXCEPTIONS TO THE OCTET RULE EXERCISE Identify each violation to the octet rule by drawing a Lewis electron dot diagram. ClO SF6

44. EXCEPTIONS TO THE OCTET RULE EXERCISE With one Cl atom and one O atom, this molecule has 6 + 7 = 13 valence electrons, so it is an odd-electron molecule. A Lewis electron dot diagram for this molecule is as follows :

45. EXCEPTIONS TO THE OCTET RULE EXERCISE In SF6, the central S atom makes six covalent bonds to the six surrounding F atoms, so it is an expanded valence shell molecule. Its Lewis electron dot diagram is as follows:

46. POLARIZATION OF COVALENT COMPOUNDS Polarity is the distribution of electrical charge over the atoms connected by the bond. For example, the hydrogen atom in hydrogen chloride is slightly positively charged, whereas the chlorine atom is slightly negatively charged .

47. POLARIZATION OF COVALENT COMPOUNDS The bond or the molecular polarities depend upon the electronegativity of the atoms or the molecules. A molecule is basically said to be either a polar molecule, non- polar molecule or ionic molecule.

48. POLARIZATION OF COVALENT COMPOUNDS

49. POLARIZATION OF COVALENT COMPOUNDS Polar Molecules: A polar molecule is usually formed when the one end of the molecule is said to possess more positive charges and whereas the opposite end of the molecule has negative charges, creating an electrical pole. When a molecule is said to have a polar bond, then the center of the negative charge will be on one side, whereas the center of positive charge will be in the different side. The entire molecule will be a polar molecule.

50. POLARIZATION OF COVALENT COMPOUNDS Non- Polar Molecules: A molecule which does not have the charges present at the end due to the reason that electrons are finely distributed and those which symmetrically cancel out each other are the non- polar molecules. In a solution, a polar molecule cannot be mixed with the non-polar molecule. For example, consider water and oil. In this solution, water is a polar molecule whereas oil behaves as a non-polar molecule. These two molecules do not form a solution as they cannot be mixed up.

51. NAMING COVALENT COMPOUNDS The prefixes are written at the beginning of the name of each element, with the exception of the prefix mono-, which is not used for the first element .

52. NAMING COVALENT COMPOUNDS The name of the second element loses one or two syllables and ends in the suffix -ide .

53. NAMING COVALENT COMPOUNDS Molecules that contain two atoms of the same element, such as oxygen gas, O2, are often given the prefix of di-. For example, O2 is sometimes called dioxygen.

54. METALLIC COMPOUNDS GENERAL CHEMISTRY 1

55. METALLIC COMPOUND Metallic bond is a term used to describe the collective sharing of a sea of valence electrons between several positively charged metal ions.

56. METALLIC COMPOUND The electron configuration of sodium is 1s22s22p63s1; it contains one electron in its valence shell. In the solid-state, metallic sodium features an array of Na+ ions that are surrounded by a sea of 3s electrons. However, it would be incorrect to think of metallic sodium as an ion since the sea of electrons is shared by all the sodium cations, quenching the positive charge.

57. METALLIC COMPOUND The three factors are: The number of electrons delocalized from the metal; the greater the number of delocalized electrons, the stronger the bond. Charge held by the metal cation; the greater the magnitude of the charge, the stronger the force of attraction between the electron sea and the cations. Size of the cation; the smaller the ionic radius, the greater the effective nuclear charge acting on the electron sea. Thus, the electron configuration of the element can be studied to predict the strength of the metallic bonding in it.

58. PROPERTIES OF METALLIC COMPOUND Electrical conductivity is a measure of the ability of a substance to allow a charge to move through it. Since the movement of electrons is not restricted in the electron sea, any electric current passed through the metal passes through it, as illustrated. When a potential difference is introduced to the metal, the delocalized electrons start moving towards the positive charge. This is the reason why metals are generally good conductors of electric current.

59. PROPERTIES OF METALLIC COMPOUND The thermal conductivity of a material is a measure of its ability to conduct/transfer heat. When one end of a metallic substance is heated, the kinetic energy of the electrons in that area increases. These electrons transfer their kinetic energies to other electrons in the sea via collisions. The greater the mobility of the electrons, the quicker the transfer of kinetic energy. Due to metallic bonds, the delocalized electrons are highly mobile, and they transfer the heat through the metallic substance by colliding with other electrons.

60. PROPERTIES OF METALLIC COMPOUND Malleability and Ductility When an ionic crystal (such as sodium chloride crystal) is beaten with a hammer, it shatters into many smaller pieces. This is because the atoms in the crystals are held together in a rigid lattice that is not easily deformed. The introduction of a force (from the hammer) causes the crystal structure to fracture, resulting in the shattering of the crystal . In the case of metals, the sea of electrons in the metallic bond enables the deformation of the lattice. Therefore, when metals are beaten with a hammer, the rigid lattice is deformed and not fractured. This is why metals can be beaten into thin sheets. Since these lattices do not fracture easily, metals are said to be highly ductile.

61. PROPERTIES OF METALLIC COMPOUND Metallic Luster When light is incident on a metallic surface, the energy of the photon is absorbed by the sea of electrons that constitute the metallic bond. The absorption of energy excites the electrons, increasing their energy levels. These excited electrons quickly return to their ground states, emitting light in the process. This emission of light due to the de-excitation of electrons attributes a shiny metallic lustre to the metal.

62. PROPERTIES OF METALLIC COMPOUND High Melting and Boiling Points As a result of powerful metallic bonding, the attractive force between the metal atoms is quite strong. In order to overcome this force of attraction, a great deal of energy is required. This is the reason why metals tend to have high melting and boiling points. The exceptions to this include zinc, cadmium, and mercury (explained by their electron configurations, which end with ns2 ). The metallic bond can retain its strength even when the metal is in its melt state. For example, gallium melts at 29.76oC but boils only at 2400oC. Therefore, molten gallium is a non volatile liquid.