Chapter 4 : Chemical bonds and Water

1. Chapter 4 :Chemical bonds and Water Prepared by : MDM NUR DIANA BT MAMAT Department of Science KPTM Kota Bharu

3. Water : The importance • All living organisms require water more than other substance • Most cells are surrounded by water and cells themselves are about 70-95% water • ¾ of earth surface is submerged in water • Water is the only substance that exist in three physical states of matter • Water is the major reason earth is habitable

4. 4.1 Structure and behavior of atom • Subatomic particles • Atomic number and atomic weight • Isotopes • Electron configuration • Electron orbital

5. Subatomic particles • Atom composed of small parts called subatomic particles • Subatomic particles • Proton (p)->positive • Neutron (n)-> neutral • Electron (e)-> negative

6. Atomic number and atomic weight • Atomic number • equal to the number of proton in the element • P=e • Atomic weight /mass number • total mass of an atom or the atomic mass. • p+n • Neutron • mass number –num. of proton

7. O F H 16 19 1 8 1 9

8. Example • Atom natrium • 23Na has 11 proton, 11 electron and 12 neutrons • Atomic weight : 23 dalton (mass number)

9. Isotopes • Atom that have same number of proton but differ number of neutron • E.g. CI CI C C 35 37 12 13 17 17 6 6

10. Isotopes have same chemical behavior, different in physical behavior • Radioactive isotopes is unstable, it can decay spontaneously • In decay, neutron is converted to a proton and electron

11. Electron configuration /electron shell Electron HYDROGEN (H) Atomic number = 1

12. NITROGEN (N) Atomic number = 7 (2.5)

13. OXYGEN (O) Atomic number = 8 (2.6)

14. Octet rule • Molecular compounds appears that a full set of electrons in the outer shell (8ĕ)

15. Electron orbital/electron configuration • An orbital is a three dimensional space where an electron spends most of Its time • Each orbital holds up TWO electron

16. 4.2 Chemical bonds and molecules • Chemical bonds : interaction between atom, may result in atoms staying together • for stability • Types of bond: • Covalent bonds • Ionic bonds • Hydrogen bonds (weak bonds) Strong bonds

17. Covalent bonds • Sharing valence electrons by two atoms to fulfill their valence shells (between non-metal) • Single • Share a pair of electron • Double • Share two pairs of electron • Strong chemical bonds • Two types • Polar • Non-polar

19. Single Double Single

20. Polar & non-polar • Polarity • Depending on their electronegativity Capability of an atom to attract the shared electrons in covalent bonds

21. Polar covalent bond • One of the atoms is bonded to a more electronegative atom • The electrons of the bond will not be shared equally

22. (- ) (- ) O H H ( + ) (+ )

23. Non-Polar covalent bond • Atoms have similar electronegativity • Electrons are shared equally • E.g. :oxygen (O2)

24. ionic bonds • Chemical bond that can often form between metal and non-metal ion • bond formed by the attraction between two oppositely charged ions. • The metal donates one or more electrons, forming a positively charged ion or cation • electrons then enter the non metal, causing it to form a negatively charged ion or anion

25. Natrium chloride/salt Na = 11 Cl =17

26. Na = 11 Cl =17

28. Hydrogen bond • weakest of all chemical attractions • form when a hydrogen atom that is covalently bonded to an electronegative atom is attracted to another electronegative atom, generally either oxygen (O) or nitrogen (N).

29. H O Electronegative atom H Hydrogen bond N H H H

30. (-) Hydrogen bond (+) H O H (-) (+) (+) (-) (-) (+)

31. Van der waals interaction • Weak • Occur only when atoms and molecules are very close together

32. Chemical bonds and molecules Covalent bond, Ionic bond, Hydrogen bond, Van derwaals forces Biological importance of weak bonds

33. Chemical bonds and molecules • Chemical bonds : interaction between atom, may result in atoms staying together • for stability • Types of bond: • Covalent bonds • Ionic bonds • Hydrogen bonds (weak bonds) Strong bonds

34. Covalent bonds • Sharing valence electrons by two atoms to fulfill their valence shells (between non-metal) • Single • Share a pair of electron • Double • Share two pairs of electron • Strong chemical bonds • Two types • Polar • Non-polar

36. Single Double Single

37. Polar & non-polar • Polarity • Depending on their electronegativity Capability of an atom to attract the shared electrons in covalent bonds

38. Polar covalent bond • One of the atoms is bonded to a more electronegative atom • The electrons of the bond will not be shared equally

39. (- ) (- ) O H H ( + ) (+ )

40. Non-Polar covalent bond • Atoms have similar electronegativity • Electrons are shared equally • E.g. :oxygen (O2)

41. ionic bonds • Chemical bond that can often form between metal and non-metal ion • bond formed by the attraction between two oppositely charged ions. • The metal donates one or more electrons, forming a positively charged ion or cation • electrons then enter the non metal, causing it to form a negatively charged ion or anion

42. Natrium chloride/salt Na = 11 Cl =17

43. Na = 11 Cl =17

45. Hydrogen bond • weakest of all chemical attractions • form when a hydrogen atom that is covalently bonded to an electronegative atom is attracted to another electronegative atom, generally either oxygen (O) or nitrogen (N).

46. H O Electronegative atom H Hydrogen bond N H H H

47. (-) Hydrogen bond (+) H O H (-) (+) (+) (-) (-) (+)

48. Van der waals interaction • Weak • Occur only when atoms and molecules are very close together

49. 4.3 Properties of water • Cohesive and adhesive • High specific heat • High heat of vaporization • Water expansion • Versatile solvent

50. Cohesive and Adhesive • Cohesive • Def : A substance that have the capacity to stick with each other tightly • Due to hydrogen bonding • Contributes to the transportation of water and nutrient against gravity in plants. • Water transport from root to leaves via a water conducting cells. • In plant • Process happening during evaporation / transpiration