Bonding Notes


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Bonding Notes

  2. 2. <ul><li>Ion – a charged particle </li></ul><ul><li>(A neutral atom becomes an ion when it loses or gains an electron, so p + ≠ e - anymore) </li></ul><ul><li>If an atom loses an electron, it becomes a positively charged ion, called a cation . ( METALS!) </li></ul><ul><ul><li>Na 1+ Ca 2+ Al 3+ </li></ul></ul><ul><li>If an atom gains an electron, it becomes a negatively charged ion, called an anion . ( NONMETALS!) </li></ul><ul><li>Cl 1- O 2- N 3- </li></ul>
  3. 3. Ionic Bonding is due to: Ionization Energy (IE) Electronegativity (EN) * Metals have relatively low IEs * Nonmetals have relatively high ENs so . . . Ionic bonding will occur between . . . Metals and Nonmetals
  4. 4. <ul><li>Since metals have low Ionization Energies, they will tend to lose their valence electrons, to obtain a stable octet, and become a cation. </li></ul><ul><li>Since nonmetals have high Electronegativities, they will tend to gain valence electrons, to obtain a stable octet, and become an anion. </li></ul><ul><li>Once the two are oppositely charged, they will be attracted to each other, and an Ionic Bond will form. </li></ul>
  5. 5. <ul><li>Ionic bonds are held together by electrostatic forces </li></ul><ul><li>The result of an ionic bond is called an ionic compound. </li></ul><ul><li>Ionic bonds form between a metal and a nonmetal atom due to large differences in electronegativity . (1.7 or greater) </li></ul><ul><li>The nonmetal’s EN is so much greater than the metal’s , that it removes the electrons, forming oppositely charged ions! </li></ul>
  6. 6. Writing Ionic Formulas 1 – Determine oxidation number the + or – charge of the ion 2 – Determine the ratio of ions necessary to make the sum of the charges equal to zero 3 – Insert subscripts to indicate the ratio of ions
  7. 7. Writing Formulas w/Transition Metals Most transition metals have more than one oxidation state Roman numerals in parentheses indicate the oxidation number Example : Fe 2+ iron (II) Fe 3+ iron (III)
  8. 8. Polyatomic Ions Writing Formulas / Naming Compounds <ul><li>A polyatomic ion is a covalent molecule that consists of more than one atom and has an ionic charge. </li></ul><ul><ul><li>(As opposed to being a neutral molecule.) </li></ul></ul><ul><li>Poly = many </li></ul><ul><li>Atomic = atoms </li></ul><ul><li>Ion = charged particle </li></ul>
  9. 9. Polyatomic Ions <ul><li>an ion made up of two or more atoms bonded together, that acts as a single unit with a net charge </li></ul><ul><ul><li>OH 1- hydroxide </li></ul></ul><ul><ul><li>NO 2 1 - nitrite </li></ul></ul><ul><ul><li>NO 3 1- nitrate </li></ul></ul><ul><ul><li>SO 3 2- sulfite </li></ul></ul><ul><ul><li>SO 4 2- sulfate </li></ul></ul><ul><ul><li>PO 4 3- phosphate </li></ul></ul><ul><ul><li>NH 4 1+ ammonium </li></ul></ul>
  10. 10. Naming Ionic Compounds 1 – Name the cation first and the anion second 2 – monoatomic cations use the element name 3 – monoatomic anions take their name with –ide for the ending 4 – Transition metals must use Roman numerals to indicate oxidation number 5 – If the compound contains a polyatomic ion, simply name the ion
  11. 11. Properties of Ionic Compounds <ul><li>form crystal structures (regular repeating patterns) </li></ul><ul><li>tend to have very high melting and boiling points </li></ul><ul><ul><ul><li>because ionic bond is so strong, so a large amount of energy is required to break it </li></ul></ul></ul><ul><li>in the solid state, they don’t conduct heat/electricity </li></ul><ul><li>in the liquid state (or when dissolved in water), they do conduct heat/electricity </li></ul><ul><ul><ul><li>because the ions are free to move </li></ul></ul></ul><ul><ul><ul><li>electrolyte – an ionic compound whose aqueous solution conducts an electric current </li></ul></ul></ul>
  12. 12. Explain why an aqueous solution of NaOH will conduct electricity. <ul><li>Use the following terms: </li></ul><ul><ul><li>dissociation </li></ul></ul><ul><ul><li>electrolyte </li></ul></ul><ul><ul><li>ion </li></ul></ul><ul><li>Include the following . . . </li></ul><ul><li>“electricity requires a flow of charged particles” </li></ul>
  13. 13. Explain why sodium and chlorine will form an ionic bond. <ul><li>Use the following terms in your explanation: </li></ul><ul><li>cation </li></ul><ul><li>anion </li></ul><ul><li>metal </li></ul><ul><li>nonmetal </li></ul><ul><li>electron configuration </li></ul><ul><li>valence electron </li></ul><ul><li>ionization energy </li></ul><ul><li>electronegativity </li></ul><ul><li>Octet Rule </li></ul><ul><li>electrostatic force </li></ul>
  14. 14. Ionic Bonding <ul><li>Example </li></ul>Na Cl To become more stable, sodium must lose one electron To become more stable, chlorine must gain one electron
  15. 15. Ionic Bonding <ul><li>Example </li></ul>Sodium loses an electron and becomes a Na +1 cation. Chlorine gains an electron and becomes a Cl -1 anion. Opposites attract, and an ionic compound is formed…NaCl Na Cl
  16. 16. Why does Na and Cl form an ionic bond? <ul><li>3.0 EN of Cl </li></ul><ul><li> - 0.9 EN of Na </li></ul><ul><li>2.1 Difference in EN </li></ul><ul><li>Difference in electronegativity is 2.1(>1.7) </li></ul><ul><li>An ionic bond will form. </li></ul><ul><li>Chlorine has a greater electronegativity, and is able to take electrons away from sodium. </li></ul>
  17. 17. Metallic Bonding <ul><li>Metals do not bond ionically, but they do share similar properties to ionic compounds. </li></ul><ul><li>Metals do not gain, lose or share their valence e - </li></ul><ul><li>Electron sea model – all metal atoms contribute their valence e - to form a “sea” of e - </li></ul><ul><li>delocalized electrons – e - in the “sea” that are free to move </li></ul>
  18. 18. <ul><li>metallic bond – is the attraction between a metal cation and the delocalized electrons that surround it </li></ul><ul><li>** the shared pool of e - in a metal explain some of the properties of metals </li></ul>
  19. 19. ions free to move in metallic bonding ionic bonds are rigid crystals
  20. 20. so . . . metallic bonding can explain metallic properties <ul><li>metals are good conductors because the delocalized e - in the electron sea are free to move, therefore they can carry a charge </li></ul><ul><li>metals are malleable and ductile because the delocalized e - in the electron sea are free to move, therefore the metal is able to change shape </li></ul>
  21. 21. <ul><li>alloys – mixtures of elements that have metallic properties </li></ul><ul><li>Brass Cu 70% </li></ul><ul><li>Zn 30% </li></ul><ul><li>Bronze Cu 70-95% </li></ul><ul><li>Zn 1-25% </li></ul><ul><li>Sn 1-20% </li></ul><ul><li>10 carat Au 42% </li></ul><ul><li>Gold Ag 12-20% </li></ul><ul><li>Cu 38-46 % </li></ul><ul><li>dental Hg 50% </li></ul><ul><li>amalgam Ag 35% </li></ul><ul><li>Sn 15% </li></ul>
  22. 22. True / False <ul><li>Metals are malleable. </li></ul><ul><li>Metals are ductile. </li></ul><ul><li>Metals conduct heat and electricity well. </li></ul><ul><li>Metals bond in a special way called metallic bonding. </li></ul><ul><li>Metallic bonding involves cations and a pool of shared electrons surrounding it. </li></ul><ul><li>The cations in a metal form a “lattice” that is held in placed by the metallic bond. </li></ul><ul><li>Metals can be drawn into thin wires without breaking because cations are still surrounded by the delocalized electrons when they shift their position in the lattice. </li></ul><ul><li>Electrons in a metal lattice are free to move. </li></ul>
  23. 23. Formula Mass <ul><li>The formula mass is the total atomic mass of a compound. </li></ul><ul><li>You can determine the formula mass by adding the individual masses of each atom in the compound . . . using the average atomic mass on the Periodic Table. </li></ul>
  24. 24. for example . . . <ul><li>H 2 O has: </li></ul><ul><ul><ul><ul><li>2 hydrogen atoms </li></ul></ul></ul></ul><ul><ul><ul><ul><li>1 oxygen atom </li></ul></ul></ul></ul><ul><li>Using the Average Atomic Mass from the Periodic Table: </li></ul><ul><li>for H (1.01 amu) x 2 = 2.02 amu </li></ul><ul><li>for O + 16.00 amu </li></ul><ul><li> 18.02 amu </li></ul>
  25. 25. Percent Composition <ul><li>The percent by mass of each element in a compound </li></ul><ul><li>Used by analytical chemists to identify the elements in a composition and their relative amounts </li></ul>mass of element X 100 = percent by mass mass of compound
  26. 26. for example . . . <ul><li>What is the percent composition of hydrogen in water? </li></ul><ul><ul><li>First assume you have exactly 1 mole of water (18.02 g) </li></ul></ul><ul><ul><li>Using the chemical formula H 2 O, you can calculate percent by mass </li></ul></ul>mass of element X 100 = percent by mass mass of compound 2.02 g H X 100 = 11.2 % H 18.02 g H 2 O
  27. 27. mass of element X 100 = percent by mass mass of compound 16.00 g O X 100 = 88.8 % O 18.02 g H 2 O NOTE : If H 2 O is: 11.2 % hydrogen by mass, it should be 88.8 % oxygen by mass.