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Chapter 4 : Chemical bonds and Water

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

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Chapter 4 : Chemical bonds and Water

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

  2. 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

  3. 4.1 Structure and behavior of atom • Subatomic particles • Atomic number and atomic weight • Isotopes • Electron configuration • Electron orbital

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

  5. 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

  6. O F H 16 19 1 8 1 9

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

  8. 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

  9. 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

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

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

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

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

  14. 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

  15. 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

  16. 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

  17. Single Double Single

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

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

  20. (- ) (- ) O H H ( + ) (+ )

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

  22. 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

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

  24. Na = 11 Cl =17

  25. 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).

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

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

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

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

  30. 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

  31. 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

  32. Single Double Single

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

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

  35. (- ) (- ) O H H ( + ) (+ )

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

  37. 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

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

  39. Na = 11 Cl =17

  40. 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).

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

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

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

  44. 4.3 Properties of water • Cohesive and adhesive • High specific heat • High heat of vaporization • Water expansion • Versatile solvent

  45. 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

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