1. Ionic, Covalent, Metallic and Hydrogen Bonds Chemical Bonding

2. Valence electrons In chemistry, valence electrons are the electrons of an atom that can participate in the formation of chemical bonds with other atoms electronsatom chemical bonds Usually the electrons found on the outermost shell

3. What holds bonded atoms together? Atoms bond when their valence electrons interact – Atoms with full outermost energy levels are less reactive (Noble Gases) – Atoms with partially filled energy levels are more reactive (Groups 1-17) Goal of atoms: have a full outer energy level

4. What holds bonded atoms together? Octet Rule: atoms tend to gain, lose, or share electrons so they have 8 electrons in their outer shell. The positively charged nucleus attracts the negatively charged electrons; this bond holds 2 atoms together. Bonds behave like flexible springs instead of like sticks

5. Electrons in Shells Electrons are placed in shells according to rules: – 1 st shell: can hold up to 2 electrons – 2 nd shell: can hold up to 8 electrons – 3 rd shell: can hold up to 18 electrons, but after 8, you move to the 4 th shell

6. Na would like to: lose 1 electron N would like to: gain 3 electrons O would like to: gain 2 electrons

8. Electron Dot Diagrams Symbols of atoms with dots to represent the valence-shell electrons (also called Lewis structures) 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 :        

9. Ionic Bonds Ionic Bond: formed when metals react with nonmetals; electrons are transferred Metals lose electrons to form POSITIVELY charged ions, or cations – Examples: Lithium, Sodium, Beryllium, Magnesium Positive ions form 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

10. Formation of Sodium Ion (Ionization) Sodium atom Sodium ion Na  – e   Na + 2-8-1 2-8 ( = Ne) 11 p + 11 p + 11 e - 10 e - 0 1 +

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

12. Some Typical Ions with Positive Charges (Cations) Group 1Group 2Group 13 H + Mg 2+ Al 3+ Li + Ca 2+ Na + Sr 2+ K + Ba 2+

13. Quick Quiz #1 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 +

14. Quiz Quiz #1 Answers 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 +

15. Quick Quiz #2 Give the ionic charge for each of the following: A. 12 p + and 10 e - 1) 02) 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-

17. Ionic Bonds Nonmetals gain electrons to form NEGATIVELY charged ions, or anions – Examples: Oxygen, Sulfur, Fluorine, Chlorine Negative ions form when the number of electrons is more than the number of protons – Group 15 nonmetals → ion -3 – Group 16 nonmetals → ion -2 – Group 17 nonmetals → ion -1

18. Ionic Bonds Electrons are transferred in ionic bonding – One atom gains electrons, and the other atoms loses electrons – Most of the time this would be members of family 1 or 2 bonding with family 17

19. Ionic Bonds Example: Sodium loses one electron to get a +1 charge (Na + ). Chlorine gains an electron to get a -1 charge (Cl - ). Then, the oppositely charged ions attract each other and form a bond.

20. Ionic Bonds

21. Ionic compounds are in the form of network structures; they therefore have high melting and boiling points because of the high amount of energy required to pull apart the bonds

22. Ionic Bonds Ratio of Ions – The chemical formula NaCl tells us there is 1 Na + ion and 1 Cl - ion, forming a neutrally charged particle. Since there is only one atom of each element, there is a 1:1 ratio – The chemical formula CaF 2 tells us there is 1 Ca +2 ion and 2 F - ions. 2 F - ions are needed to balance out the +2 charge so the particle is neutral

23. Ionic Bonds Electricity: – Solid ionic compounds don’t conduct electricity – When dissolved in water, ionic compounds conduct electricity because the ions are free to move

24. Metallic Bonds Metallic Bond: a bond formed by the attraction between positively charged metal ions and the electrons around them. – Occurs between atoms of metal elements

25. Metallic Bonds The attraction between the nucleus and the neighboring atom’s electrons holds the atoms close together Since the atoms are packed closely, the electrons move from atom to atom, which is why: – Metals conduct electricity – Metals are flexible and bend without breaking (ductile and malleable)

26. Covalent Bonds Covalent Bond: a bond formed when atoms share one or more pair of electrons – Often made of molecules – Formed between nonmetal atoms – Atoms joined by covalent bonds share electrons

28. Covalent Bonds There are 2 types of covalent bonds: – Nonpolar covalent bonds: electrons are shared equally; often occurs between 2 atoms of the same element – Polar covalent bonds: electrons are shared unequally; often occurs between 2 atoms of different elements; shared electrons are attracted to the nucleus of 1 atom more than the other Usually, electrons are more attracted to atoms of elements located to the right and closer to the top of the periodic table

29. Nonpolar Covalent Bond

30. Polar Covalent Bond Note: Partial charges occur with polar covalent bonds

31. Structural Formulas When writing structural formulas: – 1 line drawn indicates that atoms share 1 pair, or 2 electrons Example: Cl-Cl – 2 lines drawn indicate that atoms share 2 pair, or 4 electrons Example: O=O – 3 lines drawn indicate that 3 pair, or 6 electrons are being shared

32. Polyatomic Ions A polyatomic ion is an ion made of 2 or more atoms that are covalently bonded and that act like a single ion Some polyatomic anion names relate to their oxygen content – An anion ending in –ate is the ion with one more oxygen atom – An anion ending in –ite is the ion with one less oxygen atom Examples: Sulfate (SO 4 -2 ) and Sulfite (SO 3 -2 )

33. Hydrogen bonds H-bonds are weaker than covalent or ionic bonds. They form when hydrogen (with a partial positive) charge bonds to a non- hydrogen.