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Chemical Bonds

Chemical Bonds. Atom – the smallest unit of matter “indivisible”. Helium atom. electron shells. Atomic number = number of Electrons Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells.

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Chemical Bonds

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  1. Chemical Bonds

  2. Atom – the smallest unit of matter “indivisible” Helium atom

  3. electron shells • Atomic number = number of Electrons • Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells. • Electron shells determine how an atom behaves when it encounters other atoms

  4. Electrons are placed in shells according to rules: • The 1st shell can hold up to two electrons, and each shell thereafter can hold up to 8 electrons.

  5. Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons Gain 4 electrons • C would like to • N would like to • O would like to Gain 3 electrons Gain 2 electrons

  6. Why are electrons important? • Elements have different electron configurations • different electron configurations mean different levels of bonding

  7. Electron Dot Structures Symbols of atoms with dots to represent the outermost shell electrons 1 2 13 14 15 16 17 18 H He:      LiBe B  C  N  O : F :Ne :            Na Mg AlSiPS:Cl  :Ar :    

  8. Chemical bonds: an attempt to fill electron shells • Ionic bonds – • Covalent bonds – • Metallic bonds

  9. Learning Check  A. X would be the electron dot formula for 1) Na 2) K 3) Al   B.  X  would be the electron dot formula  1) B 2) N 3) P

  10. IONIC BONDbond formed between two ions by the transfer of electrons

  11. Formation of Ions from Metals • Ionic compounds result when metals react with nonmetals • Metals loseelectrons to match the number of valence electrons of their nearest noble gas • Positive ionsform when the number of electrons are less than the number of protons Group 1 metals ion 1+ Group 2 metals ion 2+ • Group 13 metals ion 3+

  12. Formation of Sodium Ion Sodium atom Sodium ion Na  – e Na + 2-8-1 2-8 ( = Ne) 11 p+ 11 p+ 11 e- 10 e- 01+

  13. Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  – 2e Mg2+ 2-8-2 2-8 (=Ne) 12 p+ 12 p+ 12 e- 10 e- 0 2+

  14. Some Typical Ions with Positive Charges (Cations) Group 1 Group 2 Group 13 H+ Mg2+ Al3+ Li+ Ca2+ Na+ K+

  15. Learning Check A. Number of valence electrons in aluminum 1) 1 e- 2) 2 e- 3) 3 e- B. Change in electrons for octet 1) lose 3e- 2) gain 3 e- 3) gain 5 e- C. Ionic charge of aluminum 1) 3- 2) 5- 3) 3+

  16. Solution A. Number of valence electrons in aluminum 3) 3 e- B. Change in electrons for octet 1) lose 3e- C. Ionic charge of aluminum 3) 3+

  17. Learning Check Give the ionic charge for each of the following: A. 12 p+ and 10 e- 1) 0 2) 2+ 3) 2- B. 50p+ and 46 e- 1) 2+ 2) 4+ 3) 4- C. 15 p+ and 18e- 2) 3+ 2) 3- 3) 5-

  18. Ions from Nonmetal Ions • In ionic compounds, nonmetals gain electrons from metals • Nonmetal add electrons to achieve the octet arrangement • Nonmetal ionic charge: 3-, 2-, or 1-

  19. Fluoride Ion unpaired electron octet 1 - : F  + e: F :  2-7 2-8 (= Ne) 9 p+ 9 p+ 9 e- 10 e- 0 1 - ionic charge

  20. Ionic Bond • Between atoms of metals and nonmetals • Bond formed by transferof electrons • Produce charged ions. Conductors and have high melting point. • Examples; NaCl, CaCl2, K2O

  21. 1). Ionic bond – electron from Na is transferred to Cl, this causes a charge imbalance in each atom. The Na becomes (Na+) and the Cl becomes (Cl-), charged particles or ions.

  22. http://www.youtube.com/watch?v=Ftw7a5ccubs

  23. COVALENT BONDbond formed by the sharing of electrons

  24. Covalent Bond • Between nonmetallic elements • Formed by sharing electron pairs • Stable non-charged particles, they are not conductors at any state • Examples; O2, CO2, C2H6, H2O, SiC

  25. Covalent Bonds

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

  27. COVALENT BONDin elements when electrons are shared equally H2 or Cl2

  28. 2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Atom Oxygen Molecule (O2)

  29. COVALENT BONDS in compounds when electrons are shared but shared unequally H2O

  30. - water is a polarmolecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

  31. METALLIC BONDbond found in metals; holds metal atoms together very strongly

  32. Metallic Bond • Formed between atoms of metallic elements • Electron cloud around atoms • Good conductors at all states, lustrous, very high melting points • Examples; Na, Fe, Al, Au, Co

  33. Ionic Bond, A Sea of Electrons

  34. Metals Form Alloys Metals do not combine with metals. They form Alloys which is a solution of a metal in a metal. Examples are steel, brass, bronze and pewter.

  35. Compounds and Their Bonds Ionic Compounds Naming Ionic Formulas

  36. Ionic Compounds • Attraction between + ions and - ions • Electrons go from metals to nonmetals electron transfer metal nonmetal ion+ ion– Electrons lost = Electrons gain

  37. Formulas of Ionic Compounds Formulas of ionic compounds are determined from the charges on the ions atoms ions  – Na  +  F :  Na+ : F :  NaF  sodium fluorine sodium fluoride formula Charge balance: 1+1- = 0

  38. Writing a Formula Write the formula for the ionic compound that will form between Ba2+ and Cl. Solution: 1. Balance charge with + and – ions 2. Write the positive ion of metal first, and the negative ion Ba2+ ClCl 3. Write the number of ions needed as subscriptsBaCl2

  39. Learning Check Write the correct formula for the compounds containing the following ions: A. Na+, S2- 1) NaS 2) Na2S 3) NaS2 B. Al3+, Cl- 1) AlCl3 2) AlCl 3) Al3Cl C. Mg2+, N3- 1) MgN 2) Mg2N3 3) Mg3N2

  40. Solution A. Na+, S2- 2) Na2S B. Al3+, Cl- 1) AlCl3 C. Mg2+, N3- 3) Mg3N2

  41. Naming Binary Ionic Compounds • Contain 2 different elements • Name the metal first, then the nonmetal as -ide. • Use name of a metal with a fixed charge Groups 1A, 2A, 3A and Ag, Zn, and Cd Examples: NaCl sodium chloride ZnI2 zinc iodide Al2O3 aluminum oxide

  42. Learning Check Complete the names of the following binary compounds: Na3N sodium ________________ KBr potassium ________________ Al2O3 aluminum ________________ MgS _________________________

  43. Solution Complete the names of the following binary compounds: Na3N sodium nitride KBr potassium bromide Al2O3 aluminum oxide MgS magnesium sulfide

  44. Learning Check A. The formula for the ionic compound of Na+ and O2- is 1) NaO 2) Na2O 3) NaO2 B. The formula of a compound of aluminum and chlorine is 1) Al3Cl 2) AlCl2 3) AlCl3 C. The formula of Fe3+ and O2- is 1) Fe3O2 2) FeO3 3) Fe2O3

  45. Solution A. The formula for the ionic compound of Na+ and O2- is 2) Na2O B. The formula of a compound of aluminum and chlorine is 3) AlCl3 C. The formula of Fe3+ and O2- is 3) Fe2O3

  46. Learning Check Name the following compounds: A. CaO 1) calcium oxide 2) calcium(I) oxide 3) calcium (II) oxide B. SnCl4 1) tin tetrachloride 2) tin(II) chloride 3) tin(IV) chloride C. Co2O3 1) cobalt oxide 2) cobalt (III) oxide 3) cobalt trioxide

  47. Solution Name the following compounds: A. CaO 1) calcium oxide B. SnCl43) tin(IV) chloride C. Co2O32) cobalt (III) oxide

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