Chemical Bonding

1. Chemical Bonding Mr. Fleming

2. Content Standards • 9.4 D.11 • Describe how atoms combine to form new substances by transferring electrons (ionic bonding) or sharing electrons (covalent bonding).

3. Significance of Chemical Bonding • Changes chemical properties of matter • Mechanism to build more complex matter • Determines how energy is transferred in a system • Energy released= Exothermic • Energy absorbed= Endothermic • Vital Chemical Reactions • Cellular Respiration= how are cells produce energy • Combustion=how we drive from point A to point B

4. Essential Questions • What are ionic and covalent bonds? • Why do bonds occur? • How do you predict what type of bond atoms will form?

5. What is Bonding? • Bonds between atoms are caused by electrons in outermost shells or valence electrons. • The process of bond formation is called a chemical reaction • Lewis-Dot Diagrams illustrate the bonding electrons within the elements doing the bonding.

7. The Rules of Bonding • Octet Rule • Elements want to fill outer shell with 8 electrons with exception of Helium and Hydrogen which want 2. • Electronegitivity • Elements ability to capture electrons • Increases as you go to top right of periodic table. (See Next Slide)

9. Electronegitivity of Periodic Table

10. Types of Bonds • Ionic • Transfer of electrons • Electrons are not shared • Na+ Cl- • Covalent • Sharing electrons • Chlorine Gas (Cl2) • Hydrogen and nonmetal like Chlorine.

11. The Ionic Bond

12. Sodium 23 Na 11 e.c. 2,8,1 11p 12n 11 protons 12 neutrons 11 electrons

13. Lewis Dot Diagram: Sodium

14. Chlorine 35 Cl 17 e.c. 2,8,7 17 protons 17p 18n 18 Neutrons 17 electrons

15. Lewis Dot Diagram: Sodium

16. + The Sodium atom has 1 Electron in it’s outer shell. Na e.c. 2,8,1 Atom The Sodium loses 1 electron to leave a complete outer shell. It is now a Sodium ion with a charge of 1 + (Na +) e.c. (2,8)+ Ion

17. - The Chlorine atom has 7 electrons in it’s outer shell. Cl e.c. 2,8,7 Atom (Cl - ) The Chlorine gains 1 electron to gain a complete outer shell. It is now a Chlorine ion with a charge of 1 - e.c. (2,8,8)- Ion

18. The Ionic Bond Chlorine atom Cl Sodium atom Na + - Sodium ion (Na +) Chlorine ion (Cl -) The sodium atom loses one electron to attain a complete outer shell and become a positive ion (Na +). The Chlorine atom gains one electron to attain a complete outer shell and become a negative ion (Cl –).Strong electrostatic forces attract the sodium and chlorine ions.

19. Lewis Dot Diagram: Na Cl

20. Ionic Compounds • Held together by strong electrostatic forces • Opposite charges attract • High melting points and boiling points • Regular structures – giant ionic lattices • When melted or dissolved ionic compounds conduct electricity

21. Examples of Ionic Compounds • Metal + Nonmetal • LiF - Lithium Fluoride • LiCl - Lithium Chloride • NaF - Sodium Fluoride • NaCl - Sodium Chloride • KBr - Potassium Bromide • KI - Potassium Iodide • CsF - Cesium Fluoride • CsCl - Cesium Chloride

22. Lewis Dot Diagram: Cl2

23. Chlorine atom 2,8,7

24. 2 Chlorine atoms Outer shells only

25. Molecular or covalent compounds are usually gases or liquids – they have low melting points and low boiling points Chlorine molecule Cl2 Electrons shared Each outer shell has 8 electrons Forces (bonds) between atoms in the molecule very strong Forces between molecules very weak Molecules have no overall electric charge

26. Covalent Bonds: Water H2O Methane CH4 Ammonia NH3 Hydrogen H2 Hydrogen Chloride HCl Oxygen O2 N.B. Oxygen has a double bond

27. 16 O 8 Oxygen Oxygen atom 2,6

28. O O 2 Oxygen atoms (outer shells only) Double covalent bond

29. Chemical Bonding Recall 1. In a chemical bond, __________ are being shared amongst different elements. Electrons 2. A _______ bond is when electrons are not being shared. Ionic

30. Chemical Bonding Recall 3. Will Lithium (Li) and Chlorine (Cl) form an ionic or covalent bond? Ionic Bond 4. Draw the resulting Lewis Dot structure that forms when lithium and chlorine bond.