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AP Chemistry

AP Chemistry. Chemical Particles. Historical Development of the Atomic Model. Greeks (~400 B.C.E.). -- Democritus Leucippus (and others). Matter is discontinuous (i.e., “grainy”). Greek model of atom. -- Plato and Aristotle disagreed, saying that matter was continuous.

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AP Chemistry

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  1. AP Chemistry Chemical Particles

  2. Historical Development of the Atomic Model Greeks (~400 B.C.E.) -- Democritus Leucippus (and others) Matter is discontinuous (i.e., “grainy”). Greek model of atom -- Plato and Aristotle disagreed, saying that matter was continuous.

  3. Hints at the Scientific Atom • -- Antoine Lavoisier: law of conservation of mass • Mass is always conserved during chemical or • physical changes. • Law of Conservation of Mass CaCl2 + Na2SO4 CaSO4 + 2NaCl mass before = mass after # atoms before = # atoms after

  4. Hints at the Scientific Atom -- Joseph Proust (1799): law of definite proportions: every compound has a fixed proportion by mass e.g., water…………………. 8 g O : 1 g H 13 g Cr : 4 g O chromium(II) oxide…..

  5. Law of Definite Proportion

  6. law of multiple proportions: When two different compounds have same two elements, equal mass of one element results in integer multiple of mass of other. e.g., water…………………….. hydrogen peroxide..……. chromium(II) oxide…….. chromium(VI) oxide……. Hints at the Scientific Atom (cont.) -- John Dalton (1803): 8 g O : 1 g H 16 g O : 1 g H 13 g Cr : 4 g O 13 g Cr : 12 g O

  7. Another Example of the Law of Multiple Proportions

  8. Atoms are not indivisible. Isotopes! NaCl, H2O, NH3, Fe2O3, C6H12O6 John Dalton’s Atomic Theory (1808) 1. Elements are made of indivisible particles called atoms. 2. Atoms of the same element are exactly alike; in particular, they have the same mass. 3. Compounds are formed by the joining of atoms of two or more elements in fixed, whole number ratios. Dalton’s model of atom e.g., 1:1, 2:1, 1:3, 2:3, 1:2:1 Dalton’s was the first atomic theory that had… evidence to support it.

  9. ATTRACTIVE REPULSIVE – + + + – – Law of Electrostatic Attraction opposite charges attract; like charge repel (also called coulombic attraction)

  10. computer monitor radar screen television -- William Crookes (1870s): “Rays” causing shadow were emitted from the cathode. Maltese cross CRT

  11. “cathode rays” electric field lines Crooke’s tube phosphorescent screen electrons -- J.J. Thomson (1897) discovered that “cathode rays” are deflected by electric and magnetic fields. He found that “cathode rays” were particles (today, we call them electrons) having a charge-to-mass ratio of 1.76 x 108Coulombs/g. + + + + + + – – – – – – (–) particles

  12. + + – + + – – + + + – – + – – – + – + + – – (plum pudding) Since atom was known to be electrically neutral, he proposed the plum pudding model. -- Equal quantities of (+) and (–) charge distributed uniformly in atom. -- (+) is ~2000X more massive than (–). Thomson’s plum pudding model

  13. x-rays -- Robert Millikan (1909) performed the “oil drop” experiment. Oil drops were given negative charges of varying magnitude. (using x-rays)

  14. Charges on oil drops were found to be integer multiples of 1.60 x 10–19C. C = coulombs. 6.40 x 10–19 C 4.80 x 10–19 C 1.60 x 10–19 C 3.20 x 10–19 C 1.60 x 10–19 C 6.40 x 10–19 C m g = q E 8.00 x 10–19 C 9.60 x 10–19 C 8.00 x 10–19 C 4.80 x 10–19 C 1.60 x 10–19 C 6.40 x 10–19 C 9.60 x 10–19 C 3.20 x 10–19 C He reasoned that this must be the charge on a single electron. He then found the electron’s mass: charge 1.60 x 10–19 C = charge per mass 1.76 x 108 C/g =9.09 x 10–28 g

  15. particle beam Ernest Rutherford (1910): Gold Leaf Experiment A beam of a-particles (+) was directed at a gold leaf surrounded by a phosphorescent (ZnS) screen. gold leaf a-source lead block ZnS screen

  16. Most a-particles passed through, some angled slightly, and a tiny fraction bounced back. Conclusions: 1. Atom is mostly empty space. (+)particles are concentrated at center. 2. nucleus = “little nut” (–) particles orbit nucleus. 3.

  17. photo from liquid H2 bubble chamber James Chadwick discovered neutrons in 1932. Purpose of Neurotn(n0) = help to bind p+ together in nucleus And now we believe in many other subatomic particles: quarks, muons, positrons, neutrinos, pions, etc.

  18. – – – – – + – + – + + – – – + + + – + – – + – – + – – + Thomson’s Plum Pudding Model Dalton’s (also the Greek) Model Rutherford’s Model N

  19. electronic charge = 1.602 x 10–19 C -- In chemistry, charges are expressed as unitless multiples of this value, not in C. e.g., 2+ (as in Ca2+), not 2 (1.602 x 10–19 C) = 3.204 x 10–19 C -- atomic mass unit (amu): used to measure masses of atoms and subatomic particles 1 p+ = 1.0073 amu 1 n0 = 1.0087 amu 1 e– = 0.0005486 amu ~ ~ i.e., mp+ = mn0 = 1 amu Conversion: 1 g = 6.02 x 1023amu

  20. Angstroms (A) are often used to measure atomic dimensions. 1 A = 1 x 10–10 m = 1 x 10–8 cm Conversion: # of protons (p+) atomic number: -- the whole number on Periodic Table; determines the identity of an atom mass number: (# of p+) + (# of n0) isotopes: different varieties of an element’s atoms same # of p+, differ #’s of n0 (thus, differ masses) -- -- some are radioactive; others aren’t -- A nucleus of a specific isotope is sometimes called a… nuclide. All atoms of an element react the same, chemically.

  21. mass # charge (if any) atomic # element symbol 125 – I 53 iodine is now added to salt Goiter due to lack of iodine Complete Atomic Designation …gives precise info about an atomic particle

  22. 238 U 92 23 + Na 11 79 2– Se 34 27 32 24 17 20 18 25 30 18 Complete Atomic Designation Protons Neutrons Electrons 92 146 92 11 12 10 34 45 36 59 3+ Co 27 37 – Cl 17 55 7+ Mn 25

  23. % abundance Average Atomic Mass (a.k.a., Atomic Mass or Atomic Weight) This is the weighted average mass of all atoms of an element, measured in a.m.u. For an element with isotopes A, B, etc.: Ti has five naturally-occurring isotopes AAM = Mass A (% A) + Mass B (% B) + … (use the decimal form of the %; e.g., use 0.253 for 25.3%)

  24. 1 “average” atom 6.02 x 1023 atoms Lithium has two isotopes. Li-6 atoms have mass 6.015 amu; Li-7 atoms have mass 7.016 amu. Li-6 makes up 7.5% of all Li atoms. Find Average atomic mass (AAM) of Li. Li batteries AAM = Mass A (% A) + Mass B (% B) AAM = 6.015 amu (0.075) + 7.016 amu (0.925) AAM = 0.451 amu + 6.490 amu AAM = 6.94 amu ** Decimal number on Table refers to… molar mass (in g) OR AAM (in amu).

  25. 0.031 0.031 % abundance Isotope Mass Si-28 27.98 amu 92.23% Si-29 28.98 amu 4.67% ? Si-30 3.10% AAM = MA (% A) + MB (% B) + MC (% C) 28.086 = 27.98 (0.9223) + 28.98 (0.0467) + X (0.031) 28.086 = 25.806 + 1.353 + 0.031X 28.086 = 27.159 + 0.031X 0.927 = 0.031X X = MSi-30 = 29.90 amu

  26. The Periodic Table group: a vertical column; elements in a group share certain phys. and chem. properties metals nonmetals metalloids -- group 1 = alkali metals -- group 2 = alkaline earth metals -- group 16 = chalcogens -- group 17 = halogens -- group 18 = noble gases

  27. F F–C–F F Molecular compounds contain only… nonmetals. empirical formula: shows relative #s of each type of atom inmolecule(CH2) molecular formula: shows actual #s & types of atoms in molecule (C3H6) structural formula: shows which atoms are bonded to which Just like a Lewis structure, but w/o unshared pairs. Also… perspective ball-and- space-filling drawing stick model model

  28. Nomenclature of Binary Molecular Compounds (two types of nonmetals bonded together) FORGET CHARGES! Use Greek prefixes to indicate how many atoms of each element, but don’t use “mono” on first element. hexa 1 – mono 6 – Also, don’t use any prefixes if H is the first element 2 – di 7 – hepta 3 – tri 8 – octa e.g., H2S- hydrogen sulfide HF- hydrogen fluoride HCl- hydrogen chloride 4 – tetra 9 – nona 5 – penta 10 – dec

  29. Naming Covalent “Formula to Name” • Elements in the order they appear in the formula • The subscripts become the prefixes the in the name The 1st Element • Write the prefix followed by the element name • The prefix mono is never used for the 1st element The 2nd Element • Write the prefix followed by the ROOT name of the element (drop the ending) and add –IDE • You mustuse the prefix mono for the 2nd element C2F4 BF3 Boron trifluoride dicarbon tetrafluoride

  30. Naming Covalent “Formula to Name” Double Vowels • oo and ao drop the 1st vowel; keep the 2nd vowel • ii and io  keep both vowels • Practice Problems Not ao Just o Carbon trichloride N2O5 Dinitrogenpentoxide CCl3 Keep io BrF Bromine monofluoride NO2 Nitrogen dioxide Keep ii Not oo Just o SI2 Sulfur diiodide Nitrogen monoxide NO

  31. Naming Covalent “Name to Formula” • Elements are written in the order that they appear in the name • The prefixes are the subscripts in the formula • NEVER REDUCEthe subscripts. Practice naming Phosphorus pentachloride PCl5 Tetraphosphorus hexoxide P4O6 Sulfur hexafluoride SF6 SO3 Sulfur trioxide SiO2 Silicon dioxide N2O3 Dinitrogen trioxide P5O10 Pentaphosphorus decoxide

  32. Covalent Molecules with Special Names! Diatomic Molecules – 7 naturally occurring N2H2F2O2I2Cl2Br2 • Never Have Fear Of Ice Cold Beverages; 7-Up • Element Name + Physical State O2 = oxygen gas Br2 = liquid bromine I2 = solid iodine Common Names (Memorize them!) NH3 = ammonia CH4 = methane C3H8 = propane

  33. Ions and Ionic Componods • Atom or a group of atom that became electrically charged • When an atom loses electron: loses (-) charge so it becomes (+) • When an atom gains electron: gains (-) charge so it becomes (-)

  34. Forming Ionic Bonds: • Electrical Attraction between 2 oppositely charged ion • When ions comes together, the charges cancels out • e- is transferred from a metal atom to a non metal atom

  35. + C ion.” A ion: a charged particle (i.e., a charged atom or group of atoms) Ions and Ionic Compounds anion: a (–) ion cation: a (+) ion -- more e–than p+ -- more protons+than e– a cation a fish formed when… atoms lose e– -- -- formed when… atoms gain e– a cat keeping anion a fish n A ions are negative ions. “When I see a cation, I see a positive ion; that is, I…

  36. Ionic Bonding just read The force of electrical attraction between 2 oppositely charged ions. Occurs after a transfer or loss/gain of electrons When ions comes together, the charges cancels out Usually form between atoms of metals and atoms of non-metals Which different groups or families of elements will most-likely interact to create these types of bonds? 1+ 1- Na Cl - Example - Sodium Chloride (NaCl)

  37. Ionic compounds, or salts, consist of oppositely-charged species bonded by electrostatic forces. You can describe salts as “metal-nonmetal,” but “cation-anion” is better.

  38. Metals always lose electrons • Metals have low ionization energy… they lose electrons easily! • The number of electrons lost is equal to the charge of the metal ion. • Metals always form + cations

  39. Metals always lose electrons continued • Type I Metals (simple) fixed they always form the SAME charge • Type II Metals (complex) varies charge they form DIFFERENT charges Same +1 Same +3 +2 Transition metals some charges are the same some are differ

  40. Oxidation Number Read only • The charge that an atom would have if it lost or gained electrons; ionic charge • Can be helpful in determining which atoms will interact or bond with each other • Example: 2+ Mg According to electron dot diagram for Magnesium, it has two valence electrons. Because Magnesium is “unhappy” with two, it will typically lose them. If this happens it will turn into a Magnesium ion. At this point it will have an oxidation number of +2.

  41. Naming Simple Metal Ions (Type I) • Neutral atoms just have their names from the periodic table… but when they are ions you must attach the word ion! Read and review… Potassium Potassium ion Mg Mg+2

  42. has neutral charge; Nomenclature of Simple Ionic Compounds chemical formula: shows types of atoms and how many of each To write an ionic compound’s formula, we need: 1. the two types of ions 2. the charge on each ion NaF Na+ and F– BaO Ba2+ and O2– Na2O Na+ and O2– BaF2 Ba2+ and F–

  43. Na Ba A. To name, given the formula: 1. Use name of cation. 2. Use name of anion (it has the ending “ide”). sodiumfluoride NaF No prefixes are used bariumoxide BaO sodium oxide Na2O barium fluoride BaF2

  44. Zn Ca B. To write formula, given the name: Ag 1. Write symbols for the two types of ions. 2. Balance charges to write formula. Ag+ Ag2S S2– silversulfide Zn2+ P3– Zn3P2 zincphosphide I– CaI2 Ca2+ calciumiodide

  45. Naming Complex Metal Ions (Type II) • Write the name of the metal and add a Roman numeral = the charge • Roman numeral allows us to tell the ions apart… like a last name! • Ex: If two people were named John you would need to know their last names to tell them apart… John Smith & John Black Fe+2Fe+3 Cu+1Cu+2 • The word ion is not necessary. The Roman numeral tells us it’s an ion Iron (II) Iron (III) Both are named iron ion Copper(I) Copper (II) Both are named copper ion

  46. Take out ionic bond handout Naming Metal Ions Zn+2 Too many choices so I can’t figure it out. The word ion is too vague. • Zinc ion • Nickel (II) • Chromium ion • Mn+4 • Sr+2 • V+5 Ni+2 Cr? Manganese (IV) Strontium ion Vanadium (V)

  47. Cu Fe A. To name, given the formula: • Figure out charge on • cation. 2. Write name of cation. 3. Write Roman numerals in ( ) to show cation’s charge. Stock System of nomenclature 4. Write name of anion. Fe2+ Fe? iron(II)oxide FeO O2– Fe? O2– Fe2O3 Fe3+ Fe? O2– O2– Fe3+ iron(III)oxide CuBr Cu? Br– copper(I)bromide Cu+ CuBr2 Br– copper(II)bromide Cu2+ Cu? Br–

  48. Co Sn B. To find the formula, given the name: 1. Write symbols for the two types of ions. 2. Balance charges to write formula. cobalt(III)chloride Co3+ Cl– CoCl3 Sn4+ O2– SnO2 tin(IV) oxide Sn2+ tin(II)oxide O2– SnO

  49. NON-METALS Always GAIN Electrons • Non-metals have a high electronegativity… they gain electrons easily! •  The # of electrons gained equals to the charge of the non-metal ion. • Non-metals always form (-) anions • Non-metals always form the SAME charge… they are simple ions! -2 -1 -3 18 13 16 15 17 14

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