Bonding Notes
- 2. Ion – a charged particle (A neutral atom becomes an ion when it loses or gains an electron, so p + ≠ e - anymore) If an atom loses an electron, it becomes a positively charged ion, called a cation . ( METALS!) Na 1+ Ca 2+ Al 3+ If an atom gains an electron, it becomes a negatively charged ion, called an anion . ( NONMETALS!) Cl 1- O 2- N 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. Since metals have low Ionization Energies, they will tend to lose their valence electrons, to obtain a stable octet, and become a cation. Since nonmetals have high Electronegativities, they will tend to gain valence electrons, to obtain a stable octet, and become an anion. Once the two are oppositely charged, they will be attracted to each other, and an Ionic Bond will form.
- 5. Ionic bonds are held together by electrostatic forces The result of an ionic bond is called an ionic compound. Ionic bonds form between a metal and a nonmetal atom due to large differences in electronegativity . (1.7 or greater) The nonmetal’s EN is so much greater than the metal’s , that it removes the electrons, forming oppositely charged ions!
- 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. 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. Polyatomic Ions Writing Formulas / Naming Compounds A polyatomic ion is a covalent molecule that consists of more than one atom and has an ionic charge. (As opposed to being a neutral molecule.) Poly = many Atomic = atoms Ion = charged particle
- 9. Polyatomic Ions an ion made up of two or more atoms bonded together, that acts as a single unit with a net charge OH 1- hydroxide NO 2 1 - nitrite NO 3 1- nitrate SO 3 2- sulfite SO 4 2- sulfate PO 4 3- phosphate NH 4 1+ ammonium
- 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. Properties of Ionic Compounds form crystal structures (regular repeating patterns) tend to have very high melting and boiling points because ionic bond is so strong, so a large amount of energy is required to break it in the solid state, they don’t conduct heat/electricity in the liquid state (or when dissolved in water), they do conduct heat/electricity because the ions are free to move electrolyte – an ionic compound whose aqueous solution conducts an electric current
- 12. Explain why an aqueous solution of NaOH will conduct electricity. Use the following terms: dissociation electrolyte ion Include the following . . . “electricity requires a flow of charged particles”
- 13. Explain why sodium and chlorine will form an ionic bond. Use the following terms in your explanation: cation anion metal nonmetal electron configuration valence electron ionization energy electronegativity Octet Rule electrostatic force
- 14. Ionic Bonding Example Na Cl To become more stable, sodium must lose one electron To become more stable, chlorine must gain one electron
- 15. Ionic Bonding Example 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. Why does Na and Cl form an ionic bond? 3.0 EN of Cl - 0.9 EN of Na 2.1 Difference in EN Difference in electronegativity is 2.1(>1.7) An ionic bond will form. Chlorine has a greater electronegativity, and is able to take electrons away from sodium.
- 17. Metallic Bonding Metals do not bond ionically, but they do share similar properties to ionic compounds. Metals do not gain, lose or share their valence e - Electron sea model – all metal atoms contribute their valence e - to form a “sea” of e - delocalized electrons – e - in the “sea” that are free to move
- 18. metallic bond – is the attraction between a metal cation and the delocalized electrons that surround it ** the shared pool of e - in a metal explain some of the properties of metals
- 19. ions free to move in metallic bonding ionic bonds are rigid crystals
- 20. so . . . metallic bonding can explain metallic properties metals are good conductors because the delocalized e - in the electron sea are free to move, therefore they can carry a charge 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
- 21. alloys – mixtures of elements that have metallic properties Brass Cu 70% Zn 30% Bronze Cu 70-95% Zn 1-25% Sn 1-20% 10 carat Au 42% Gold Ag 12-20% Cu 38-46 % dental Hg 50% amalgam Ag 35% Sn 15%
- 22. True / False Metals are malleable. Metals are ductile. Metals conduct heat and electricity well. Metals bond in a special way called metallic bonding. Metallic bonding involves cations and a pool of shared electrons surrounding it. The cations in a metal form a “lattice” that is held in placed by the metallic bond. 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. Electrons in a metal lattice are free to move.
- 23. Formula Mass The formula mass is the total atomic mass of a compound. 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.
- 24. for example . . . H 2 O has: 2 hydrogen atoms 1 oxygen atom Using the Average Atomic Mass from the Periodic Table: for H (1.01 amu) x 2 = 2.02 amu for O + 16.00 amu 18.02 amu
- 25. Percent Composition The percent by mass of each element in a compound Used by analytical chemists to identify the elements in a composition and their relative amounts mass of element X 100 = percent by mass mass of compound
- 26. for example . . . What is the percent composition of hydrogen in water? First assume you have exactly 1 mole of water (18.02 g) Using the chemical formula H 2 O, you can calculate percent by mass 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. 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.