Atom – the smallest unit of matter “indivisible”

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

2. 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

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

4. 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

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

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

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

9. Ionic Bond • Between atoms of metals and nonmetals with very different electronegativity • Bond formed by transfer of electrons • Produce charged ions all states. Conductors and have high melting point. • Examples; NaCl, CaCl2, K2O

11. Ionic Bonds: One Big Greedy Thief Dog!

12. 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.

14. COVALENT BONDbond formed by the sharing of electrons

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

16. Covalent Bonds

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

18. NONPOLAR COVALENT BONDS when electrons are shared equally H2 or Cl2

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

20. POLAR COVALENT BONDS when electrons are shared but shared unequally H2O

21. Polar Covalent Bonds: Unevenly matched, but willing to share.

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

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

24. 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

25. Metallic Bonds: Mellow dogs with plenty of bones to go around.

26. Metallic Bonds, A Sea of Electrons

27. A polar bond is a bond in which the bonding electron pair is shared unequally. A polar molecule is a molecule with regions of partial negative (d –) and partial positive (d +) charge.

28. The degree of sharing (equal to unequal) is determined by the electronegativity difference between the two atoms.

30. F F Two atoms of equal electronegativity will share the bond equally

31. H Cl 3.0 2.1 Two atoms with a small difference in electronegativity will share unequally, resulting in partial charge.

32. d + d – H Cl Two atoms with a small difference in electronegativity will share unequally, resulting in partial charge.

33. d + d – H Cl This is a polar bond: The bonding pair is, on average, closer to one atom.

34. d + d – H Cl

35. d + d – H Cl Yes it is!

36. 4.0 0.8 K F Two atoms with a large difference in electronegativity will result in a loss of an electron, resulting in a full charge. This is an ionic bond and not a covalent bond

37. K F

38. K F

39. K F

40. K F

41. K F

42. K F

43. _ + K F positive ion negative ion

44. A polar bond in a molecule may make the entire molecule polar, with one end slightly positive and the other end slightly negative.

45. d + H Cl d – Hydrogen chloride is an example of a polar molecule.

46. The SHAPE of the molecule determines whether its polar bonds make the molecule polar

47. In CF4 the fluorines are symmetrically arranged around the carbon.

48. The fluorines all pull on the valence electrons in opposite directions, effectively cancelling out the polarity of the bonds

49. CF4 has four polar bonds but it is a non-polar molecule: There is no partial charge on the molecule.

50. The two hydrogens of water are not symmetrically positioned around the oxygen.