Chemical Bonding

1. Chemical Bonding No one wants to be alone

2. Why atoms bond • Most atoms are not found alone in quantity in the universe, they are bonded to other atoms • All atoms except the ones in Group 18 (the Noble Gases) have an unstable electron configuration • Atoms will gain, lose, or share valence electrons until they become stable

3. Rule of Octet • The major groups of the Periodic Table (Groups 1, 2, 13, 14, 15, 16, 17) will gain, lose, or share electrons until they have 8 or 0 valence electrons • 0 valence electrons means that layer is stripped and the full inner layer is exposed, making them stable

4. Counting outer shell electrons • An Electron-Dot Diagram allows us to draw atoms and show their valence electron configuration • Write the element’s symbol • Begin placing dots around the symbol equal to the number of outer-shell electrons • 1 to a side, then double up

5. Oxidation Numbers • The charge on the atom after an atom gains, loses, or shares electrons to become stable • This positive or negative number tells you how many electrons the atom gained or lost

6. +3 ±4 -3 -2 -1 Ø +1 +2

7. How many valence electrons does Magnesium have? • 1 • 2 • 3 • 4 • 5

8. How many valence electrons will Magnesium gain, lose, or share? • Lose 1 • Gain 1 • Lose 2 • Gain 2 • Gain 6

9. What is Magnesium’s Oxidation Number? • +1 • -1 • +2 • -2 • -6

10. What is Chlorine’s Oxidation Number? • +1 • -1 • +2 • -2 • +7

11. What is Potassium’s Oxidation Number? • +1 • -1 • +2 • -2 • -3

12. What is Sulphur’s Oxidation Number? • +1 • -1 • +2 • -2 • +3

13. Ions • When an atom gains or loses electrons, it now has a charge • A charged particle is called an ion • Atoms losing electrons have a positive charge and are called anions • Atoms gaining electrons have a negative charge and are called cations

14. Types of Chemical Bonding • Ionic Bonds are formed: • When one atom (usually a metal) loses 1 or more electrons and • Another atom (usually a nonmetal) gains 1 or more electrons • The attraction between positive and negative ions (opposites attract) causes the atoms to stick together with an incredible amount of electromagnetic force

15. More on Ionic Bonds • Ionic Bonds • Are created from elements on opposite sides of the Periodic Table • Have unusually high melting and boiling points • Are usually solids at room temperature • Dissolve into aqueous solutions easily (soluble or miscible)

16. Types of Chemical Bonding • Covalent Bonds are formed: • When two or more atoms share outer-shell electrons to complete their octet • Once the sharing begins, the atoms can not go their different ways except to take the electrons that they were sharing and bond to another atom

17. More on Covalent Bonds • Covalent Bonds • Are created from elements somewhat close to each other on the Periodic Table • Can be liquids or solids at room temperature • Many do not dissolve into aqueous solutions easily (immiscible)

18. Types of Chemical Bonding • Metallic Bonds are formed: • When one or more metals combine (alloy) • The positive nuclei arrange into a lattice, while the electrons flow freely from atom to atom • Sometimes called a “Sea of Electrons”

19. More on Metallic Bonds • Metallic Bonds • Explains why metals are lustrous and good conductors of electricity (the flow of electrons) • Are solids at room temperature • May lose electrons to substances outside of the bond, causing corrosion or oxidation of the metals (rusting) • Usually with Oxygen, forms a nonmetallic compound and substantially weakens the metals

20. Bonds and Polarity • Electronegativity • Describes how “stingy” an atom is towards electrons • Increases as you move up and right on the Periodic Table

21. General Reactivity • Reactivity increases for Metals as you move down and left from the stair-step • Reactivity increases for Nonmetals as you move up and right from the stair-step • Fluorine is the most reactive nonmetal, Cesium or Francium is the most reactive metal

22. Covalent Bonds and Polarity • Polar Covalent Bonds • Formed when the atoms in a sharing relationship don’t share evenly • A slight negative charge appears on the end of the molecule with the “Stingy” atom • A slight positive charge appears on the end of the molecule with the “Generous” atom

23. Solubility and Polarity • “Like dissolves like” • Polar molecules can dissolve other polar molecules • Polar molecules can dissolve ionic molecules • Nonpolar molecules can dissolve other nonpolar molecules • Polar substances can not dissolve nonpolar substances • Nonpolar substances can not dissolve polar substances

24. REVIEW • Metallic Bonds • Electronegativity • Reactivity • Polarity • Solubility • Why atoms bond • Rule of Octet • Exceptions! • Electron-Dot Diagrams • Oxidation Numbers • Ions • Ionic Bonds • Covalent Bonds

25. Most atoms bond because • They’re lonely • They have too many valence electrons • They have too few valence electrons

26. What number of outer shell electrons is stable for most atoms? • 2 • 8 • 0 • 6 • 2 & 8 • 8 & 0 • 0 & 6

27. What do we use to show just the valence electrons for an atom? • Bohr model • Wave model • Scale model • Electron Dot Diagram

28. What is the name for an atom that has gained or lost electrons? • Positron • Ion • Negatron • Megatron

29. How do atoms become stable? • Gain electrons • Lose electrons • Share electrons • All of the above

30. Atoms that have gained electrons are called? • Ion • Anion • Positron • Cation

31. Ionic bonds are held together by which force? • Strong nuclear • Weak nuclear • Electromagnetic • Gravity

32. Atoms that have lost electrons are called? • Ion • Anion • Positron • Cation

33. Covalent bonds are formed when atoms • Gain electrons • Lose electrons • Share electrons • All of the above

34. Atoms far apart on the Periodic Table will usually bond • Ionically • Covalently • Metallically • They will not bond

35. Groups 3 – 12 will use which method to bond? • Ionic bonding • Covalent bonding • Metallic bonding • They will not bond

36. Which part of a metallic bond explains why metals are lustrous and good conductor of electricity? • Nuclei in a lattice • “Sea of electrons” • The density of the nuclei • Metals aren’t good conductors

37. Atoms with a strong attraction to their electrons are said to be • Positronic • Gravometric • Thaleonic • Electronegative

38. What is the most reactive nonmetal? • Chlorine • Fluorine • Oxygen • Sulphur

39. A covalent bond where the atoms do not share evenly is called a • Polar Bond • Equatorial Bond • Longitudinal Bond • Latitudinal Bond

40. What is the rule concerning how polar and nonpolar bonds react? • “Opposites Attract” • “Like Repel” • “Like dissolves like” • “Bless the Maker and his Water”

41. Most atoms are found _____ in nature. • Bonded • Unbonded • Free • Free-range

42. What is the most electronegative (stingiest for electrons) element? • Oxygen • Chlorine • Fluorine • Arsenic

43. How does oxidation affect a metal? • Strengthens it • Weakens it • Makes it useful

44. A covalent bond where the atoms share evenly is called a • Polar Bond • Nonpolar Bond • Ionic Bond • Metallic Bond

45. Draw the Electron-Dot diagram for Selenium (Group 16, Period 4, Atomic # 34).

46. Which group of elements loses electrons most easily? • 1. Group 3 • 2. Group 15 • 3. Group 1 • 4. Group 17

47. In an electron-dot diagram of oxygen (O), how many dots should be drawn around the element’s symbol? WHY?

48. Explain why the Noble Gases (Group 18) will not bond ionically, covalently, or metallically.

49. Compare a covalent bond and an ionic bond.

50. Describe why water will dissolve sugar easily, but sugar will not dissolve in cooking oil.