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CHAPTER 2

CHAPTER 2. ATOMS and MOLECULES. Periodic Table. Atomic Mass number below the element not whole numbers because the masses are averages of the masses of the different isotopes of the elements. Ions. Are charged species Result when elements gain electrons or lose electrons.

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CHAPTER 2

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  1. CHAPTER 2 ATOMS and MOLECULES

  2. Periodic Table • Atomic Mass • number below the element • not whole numbers because the masses are averages of the masses of the different isotopes of the elements

  3. Ions • Are charged species • Result when elements gain electrons or lose electrons

  4. 2 Types of Ions • Anions – (-) charged • Example: F- • Cations – (+) charged • Example: Na+

  5. Highly Important! • Gain of electrons makes element (-) = anion • Loss of electrons makes element (+) = cation

  6. Charges • When elements combine, they have to be in the form of IONS. • Cations and anions combine to form compounds. • For a neutral compound, the sum of the charges must be ZERO. • For a polyatomic ion, the sum of the charges must equal the charge of the ION.

  7. Isotopes • Are atoms of a given element that differ in the number of neutrons and consequently in atomic mass.

  8. Example Isotopes % Abundance 12C 98.89 % 13C 1.11 % 14C 11C

  9. For example, the mass of C = 12.01 a.m.u is the average of the masses of 12C, 13C and 14C.

  10. Determination of Aver. Mass • Ave. Mass = [(% Abund./100) (atomic mass)] + [(% Abund./100) (atomic mass)]

  11. Take Note: • If there are more than 2 isotopes, then formula has to be re-adjusted

  12. Sample Problem 1 • Assume that element Uus is synthesized and that it has the following stable isotopes: • 284Uus (283.4 a.m.u.) 34.6 % • 285Uus (284.7 a.m.u.) 21.2 % • 288Uus (287.8 a.m.u.) 44.20 %

  13. Solution • Ave. Mass of Uus = • [284Uus] (283.4 a.m.u.)(0.346) • [285Uus] +(284.7 a.m.u.)(0.212) • [288Uus] +(287.8 a.m.u.)(0.4420) • = 97.92 + 60.36 + 127.21 • = 285.49 a.m.u (FINAL ANS.)

  14. Oxidation Numbers • Is the charge of the ions (elements in their ion form) • Is a form of electron accounting • Compounds have total charge of zero (positive charge equals negative charge)

  15. Oxidation States • Are the partial charges of the ions. Some ions have more than one oxidation states.

  16. Oxidation States • - generally depend upon the how the element follows the octet rule • Octet Rule – rule allowing elements to follow the noble gas configuration

  17. Nomenclature • - naming of compounds

  18. Periodic Table • Rows (Left to Right) - periods • Columns (top to bottom) - groups

  19. Rule 1 – IONIC COMPOUNDS • Metals w/ Fixed Oxidation States • Name metal or first element asis - Anion always ends in “–ide”

  20. Terminal element or anion • O - oxide P - phosphide • N - nitride Se - selenide • S - sulfide Cl - chloride • F - fluoride I - iodide • Br - bromide C - carbide

  21. Note • Only elements that come directly from the periodic table WILL end in –IDE. • POLYATOMIC IONS will be named AS IS.

  22. Name the following: • CaO- • NaCl - • MgO - • CaS - • Na3N -

  23. Answers: • CaO- calcium oxide • NaCl - sodium chloride • MgO - magnesium oxide • CaS - calcium sulfide • Na3N - sodium nitride

  24. Where do the subscripts come from? • Answer: From the oxidation states of the ions. • Remember: Ions are the species that combine. • Target: Compounds! (No charges!)

  25. Second Rule • II. Ionic Compounds - Metals with no fixed oxidation states (Transition Metals) except for Ag, Zn and Al • Metal(Roman #) + 1st syllable + ide • Use Roman numerals after the metal to indicate oxidation state

  26. Name the following: • Copper (I) sulfide • Iron (II) oxide • Tin (II) iodide • Iron (III) nitride

  27. Answers: • Copper (I) sulfide Cu2S • Iron (II) oxide FeO • Tin (II) iodide SnI2 • Iron (III) nitride FeN

  28. What about…….? • Cesium hydroxide • Iron (III) acetate • Lithium phosphate • Aluminum Sulfite • Lead (II) sulfate • Silver nitrate

  29. POLYATOMIC IONS • Consist of more than 1 element. • Have charges. • Ex. SO42-, SO32-, PO43-,PO33-

  30. Rule 3 – Covalent Compounds • III. For Non-metals (grps IV, V, VI VII), use prefixes. Mono – 1 Hepta - 7 Di - 2 Octa - 8 Tri – 3 Nona - 9 Tetra – 4 Deca - 10 Penta – 5 Hexa - 6

  31. Rule 3 – Covalent Compounds (only have Non- Metals) • Name 1st element as is. Use prefix, if necessary. • Prefix + 1st element + prefix + 1st syllable of anion + ide

  32. Name the following compounds • CO2 - carbon dioxide • N2O – dinitrogen oxide • SO3 – sulfur trioxide • N2O5 – dinitrogen pentoxide • P2S5 – diphosphorus pentasulfide • CO – carbon monoxide

  33. Naming Acids • I. Acids without Oxygen • Use hydro + 1st syllable + “- ic acid” • Example: HCl = hydrochloric acid HCN = hydrocyanic acid HBr = hydrobromic acid

  34. II. Acids with oxygen • Polyatomic “ate” converts to “ic” + acid • Polyatomic “ite” converts to “ous” + acid - H2SO3 sulfurous acid • H2SO4 sulfuric acid • HNO3 nitric acid • HNO2 nitrous acid • H3PO4 phosphoric acid

  35. Trick! • If anion ends in “ – ate”, acid ends in “ – ic” • Example: • HClO4 perchlorate perchloric acid • HClO3 chlorate chloric acid

  36. Trick! • If anion ends in “ – ite”, acid ends in “ – ous” • Example: • HClO2 chlorite chlorous acid • HClO hypochlorite hypochlorous acid

  37. Name the following: • HBrO4 (perbromate) • HBrO3 (bromate) • HBrO2 (bromite) • HBrO (hypobromite)

  38. Pure Acids (not diluted) • Simply use Rule 3. Use prefixes, if necessary.

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