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___Unsaturated sugar water ___Ketchup ___Insoluble PbI2 in water
Identify each as HOMOgeneous (HO) or HETEROgeneous (HE); ___Unsaturated sugar water ___Ketchup ___Insoluble PbI2 in water ___Brass ___Chunky llama snot HO ? HO HE HO HE
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Chapter 2 Atoms, Molecules, and Ions
John D. Bookstaver St. Charles Community College St. Peters, MO 2006, Prentice Hall, Inc. “Tweaked” by Robert Hernandez Seabreeze Highschool 2015
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Atomic Theory of Matter
Originally proposed by Democritus… But ignored for 2,500 years… Because Aristotle had a DIFFERENT idea… Earth, Wind, Fire, Water… Alexander was Aristotle’s student… Alexander was kind of a big deal. John Dalton ( ) atoms are smallest, same are identical and diff are diff, not created or destroyed in chem rxns (how are they created?), compounds can form from elements and have same #s and kind of elements (Law of…) 3
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Atomic Theory of Matter
atoms are the fundamental building blocks of matter reemerged in the early 19th century, championed by John Dalton. Dalton’s Atomic Theory -smallest -same atoms are identical -not changed in chem rxns -consistent compounds form John Dalton ( ) atoms are smallest, same are identical and diff are diff, not created or destroyed in chem rxns (how are they created?), compounds can form from elements and have same #s and kind of elements (Law of…) Democritus was right!
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Law of Constant Composition
Also known as the law of definite proportions. The elemental composition of a pure substance never varies. 2 H’s and 1 O is ALWAYS water. Water is ALWAYS 2 H’s and 1 O.
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Law of Conservation of Mass
The total mass of substances present after a chemical process is the same as the mass of substances present before the process took place. 2 2 ___H2 + ___O ___H2O 1 1 1 1 1 16 Why we balance equations. 1 16 16 16 1 1 =
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The Atom, circa 1900: “plums” “Plum pudding” model, by JJ Thomson.
Do This… On your notes, draw in the “plums”. The Atom, circa 1900: “plums” “Plum pudding” model, by JJ Thomson. Positive sphere of matter (pudding) with negative electrons (plums) imbedded in it. “puddin’”
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The Electron Streams of negatively charged particles were found to emanate from cathode tubes.
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Discovery of the Electron
How Thomson did it… Dx- = e- / m- +++ Dx- H2 Dx+ - - - Dx+ = e+ / m+ m- Dx- = ___ Dx+ |e+| = |e-| mH+ m+
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Radioactivity + - +++ - - -
Using a similar setup, replacing the hydrogen with a radioactive emitter… +++ H2 - - - Ernest Rutherford discovered three types of radiation: Charge… Alpha particles Beta particles Gamma rays + -
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Discovery of the Nucleus
Ernest Rutherford shot particles at a thin sheet of gold foil and observed the pattern of scatter of the particles. Discuss.
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Rutherford’s Gold Foil Experiment
? Rutherford’s Gold Foil Experiment RaBr2 + Rutherford took a chunk of lead... A decent radiation insulator He borrowed radium bromide… From his friend Marie Curie… RaBr2 emits a particles… Positively charged Helium nuclei (He+2) Which can be detected by a device his friend Hans Geiger invented. Rutherford detected ~132,000 hits per minute. 132000
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Rutherford’s Gold Foil Experiment
132000 Rutherford then inserted a VERY THIN piece of gold foil along the a particles’ path… Only 1 x 10-6 meters… 1 micron (1m) human hair diameter = 100m Rutherford detected ~132,000 hits per minute. No change… As if the Gold wasn’t there…
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Rutherford’s Gold Foil Experiment
20 132000 But when the detector was slid… .. ricochets were detected… Not a lot, ~20 hits per minute. The Gold was there after all.
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Rutherford’s Gold Foil Experiment
132000 20 Proportion of impacts = = 2 x 10-4 132,000
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The Nuclear Atom 1x 10-4 Ao Nucleus = 1 x 10-14m
Atom Diameter = 1 x 10-10m 1 Ao Must have deflected off large massive particles, Since some particles were deflected at large angles, Thompson’s model could not be correct.
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Rutherford’s Gold Foil Experiment
Actually performed with X-Ray paper Repeated with Platinum, Silver, etc…
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Try it out! Figure out the shape of the target using the deflections of the beams… 2 1 2 3 1 1 1 2 2 3 3 4 4 5 5 4 3 4
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Rutherford’s Findings
Most of the particles passed right through A few particles were deflected VERY FEW were greatly deflected “Like howitzer shells bouncing off of tissue paper!” Conclusions: The nucleus is small The nucleus is dense The nucleus is positively charged
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Mass Spectrometry atomized, ionized element sample magnetic field
Signal Intensity Using colored pencils, fill in the diagram and graph on your notes. Atomic Mass
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isotopes separated by difference in mass
Mass Spectrometry atomized, ionized magnetic field element sample isotopes separated by difference in mass ~75% ~25% WS 2a (35)(~0.75) + (37)(~0.25) = ?
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Elements are symbolized by one or two letters.
Symbols of Elements Mass Number the total number of PROTONS and NEUTRONS in the atom. 12 C 6 Atomic Number (Z) Number of PROTONS in an element. All atoms of the same element have the same number of PROTONS. Elements are symbolized by one or two letters.
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Isotopes: Atoms of the same element with different masses. Isotopes have different numbers of neutrons. 11 6 C 12 6 C 13 6 C 14 6 C What are 3 isotopes of H (protium, deuterium, tritium) draw on board, deut and trit for fusion
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Isotopes: Isotopes are atoms of the same element having different masses due to varying numbers of neutrons. Isotope Protons Electrons Neutrons Nucleus Hydrogen–1 (protium) 1 Hydrogen-2 (deuterium) Hydrogen-3 (tritium) 2
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Average Mass Avg. Mass = (Mass1)(%) + (Mass2)(%) …
Average mass is calculated from the isotopes of an element weighted by their relative abundances. chlorine-35 (34.97), which has a natural abundance of 75.53%, and chlorine-37 (36.96), which has a natural abundance of 24.47%. Show example of weighted average at mass 75% + 25%) = 35.5 (34.97)(0.7553) + (36.96)(0.2447) = 35.45 Avg. Mass = (Mass1)(%) + (Mass2)(%) …
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1H 2H 3H Hydrogen = 1.0078 1.01 Hydrogen = + + Hydrogen = 1.0078
Atomic mass is the average of all the naturally isotopes of that element. Sig-Figs Hydrogen = 1.01 Isotope Symbol nucleus % in nature Hydrogen-1 1H 1 proton 0 neutrons 99.985% Hydrogen-2 2H 1 protons 1 neutrons 0.15% Hydrogen-3 3H 2 neutrons <0.00% Hydrogen = 1(0.999) 2(0.0015) 3(0.00) Hydrogen =
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Carbon = 12.013 12.01 Carbon = + + 14(0.0001) Carbon = 12.012
What is the atomic mass of Carbon? Sig-Figs Carbon = 12.01 Isotope Symbol nucleus % in nature Carbon-12 12C 6 protons 6 neutrons 98.89% Carbon-13 13C 7 neutrons 1.11% Carbon-14 14C 8 neutrons <0.01% Carbon = 14(0.0001) 12(0.9889) 13(0.0111) Carbon = 27
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Atomic Number Element # of protons Atomic # (Z) Carbon 6 Phosphorus 15
Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element. Element # of protons Atomic # (Z) Carbon 6 Phosphorus 15 Gold 79 = = =
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Mass Number Nuclide p+ n0 e- Mass #
Mass number is the number of protons and neutrons in the nucleus of an isotope. Mass # = p+ + n0 Nuclide p+ n0 e- Mass # Oxygen - 10 - 33 42 - 31 15 18 8 8 18 Arsenic 75 33 75 Phosphorus 16 15 31 Complete the table using the periodic table… and your BRAIN!
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Periodic Table: How are the elements arranged? Used to be by at. mass and repeated properties were seen, now better by at. #.
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Periodicity Reactivities are based on valence electrons! chemical properties of elements, display a repeating pattern of reactivities.
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Periodic Table The rows on the periodic chart are periods.
Columns are groups. Elements in the same group have similar chemical properties. Why do they have similar props? (same val #) (electrons are the deciding factor of reactivity)
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Groups These FOUR groups are known by their names.
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Periodic Table Metals are on the left side. Nonmetals are on
the right side. H (except H). Al Po Metalloids border the stair-step EXCEPT Al and Po
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Molecular Compounds Molecular compounds almost always contain only nonmetals. Molecular compounds form COVALANT bonds.
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Diatomic Molecules “H-air-ogens” H N O F Cl 2 2 2 2 2 2 2 Br I
Seems like all gases, why not noble gases? (have octet already) These seven elements occur naturally as molecules containing two atoms.
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Types of Formulas Empirical formulas give the lowest whole-number ratio of atoms of each element in a compound. Molecular formulas give the exact number of atoms of each element in a compound. emp. CH3 mol. C2H6 More on these in Chp 3
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Naming Molecular Compounds
Prefix Meaning Mono 1 Di Tri 3 4 Penta 5 Hexa 6 Hepta Octo 8 9 Deca 10 2 Tetra 7 Nona
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Naming Molecular Compounds
diphosphorus pentoxide CCl4 - carbon tetrachloride CO - carbon monoxide N2O - dinitrogen monoxide
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Ions When atoms lose or gain electrons, they become ions.
Cations are positive and are formed by elements on the left side of the periodic chart. Anions are negative and are formed by elements on the right side of the periodic chart.
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Ionic Bonds Ionic compounds (such as NaCl) are generally formed between metals and nonmetals.
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Writing Ionic Formulas
-3 Mg N Mg N +2 3 2 Because compounds are electrically neutral, one can determine the formula this way: The charge on the cation becomes the subscript on the anion. The charge on the anion becomes the subscript on the cation. If these subscripts are not in the lowest whole-number ratio, divide them by the Greatest Common Factor . Do Al and SO4 on board
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Common Cations Group 1, 2, 3 charges
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Common Anions Group 7, 6, 5 charges
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Polyatomic Ions YOU MUST KNOW…
Ammonium NH4 + nitrite NO2 - 1 nitrate NO3 - 1 sulfate SO4 - 2 sulfite SO3 – 2 ThioSulfate S2O3-2 Thiocyanate SCN- carbonate CO3 - 2 acetate C2H3O2 - 1 citrate C6H5O7-3 cyanide CN - borate BO3 -3 orthosilicate SiO4 -4 peroxide O2 - 2 hydroxide OH - hypochlorite ClO - 1 chlorite ClO2 - 1 chlorate ClO3 - 1 perchlorate ClO4 - 1 phosphate PO4 - 3 pyrophosphate P2O7 -4
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Patterns in Oxyanion Nomenclature
When there are two oxyanions involving the same element: The one with fewer oxygens ends in -ite NO2− nitrite SO32− sulfite The one with more oxygens ends in -ate NO3− nitrate SO42− sulfate
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Patterns in Oxyanion Nomenclature
The one with the fewest oxygens has the prefix hypo- and ends in -ite ClO− hypochlorite The one with the most oxygens has the prefix per- and ends in -ate ClO4− perchlorate
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Patterns in Oxyanion Nomenclature
Name Number of oxygen atoms per(element)ate (element)ate (element)ite hypo(element)ite If only two members, the endings are –ite and –ate. More O’s
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Ionic Nomenclature Write the name of the cation.
If anion is an element, change ending to –ide or write the name of the polyatomic ion. If the cation can have multiple charges, write the charge as a Roman numeral in parentheses. Iron (II) chloride, FeCl3 “Naming” FeCl2 Iron (III) chloride
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Writing Ionic Compound Formulas
Example: Barium nitrate 1. Write the formulas for the cation and anion, including CHARGES! Ba+2 ( ) NO3- 2. Check to see if charges are balanced. 2 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced!
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Writing Ionic Compound Formulas
Example: Ammonium sulfate 1. Write the formulas for the cation and anion, including CHARGES! ( ) NH4+ SO4-2 2. Check to see if charges are balanced. 2 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced!
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Writing Ionic Compound Formulas
Example: Iron(III) chloride 1. Write the formulas for the cation and anion, including CHARGES! Fe3+ Cl- 2. Check to see if charges are balanced. 3 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced!
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Writing Ionic Compound Formulas
Example: Aluminum sulfide 1. Write the formulas for the cation and anion, including CHARGES! Al3+ S2- 2. Check to see if charges are balanced. 2 3 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion. Not balanced!
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Writing Ionic Compound Formulas
Mg2+ CO32- Example: Magnesium carbonate 1. Write the formulas for the cation and anion, including CHARGES! They are balanced! 2. Check to see if charges are balanced.
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Writing Ionic Compound Formulas
Example: Zinc hydroxide NOTE: Zinc is ALWAYS +2 1. Write the formulas for the cation and anion, including CHARGES! ( ) Zn2+ OH- 2 2. Check to see if charges are balanced. Not balanced! 3. Balance charges , if necessary, using subscripts. Use parentheses if you need more than one of a polyatomic ion.
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Writing Ionic Compound Formulas
Example: Aluminum phosphate 1. Write the formulas for the cation and anion, including CHARGES! Al3+ PO43- 2. Check to see if charges are balanced. They ARE balanced!
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Naming Ionic Compounds
CaCl2 1. Cation first, then anion 2. cation = name of the element Ca2+ = calcium ion 3. anion = root + -ide Cl- = chloride CaCl2 = calcium chloride
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Naming Ionic Compounds
PbCl2 Metals with multiple oxidation states some metal forms more than one cation use Roman numeral in name, PbCl2 Pb2+ is the lead (II) cation PbCl2 = lead (II) chloride
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Which Big Ideas did this chapter address?
Structure of Matter: The chemical elements are fundamental building materials of matter, and all matter can be understood in terms of arrangements of atoms. These atoms retain their identity in chemical reactions 2. Properties of Matter: Chemical and physical properties of materials can be explained by the structure and the arrangement of atoms, ions, or molecules and the forces between them. 3. Chemical Reactions: Changes in matter involve the rearrangement and/or reorganization of atoms and/or the transfer of electrons 4. Rates of Chemical Reactions: Rates of chemical reactions are determined by details of the molecular collisions. 5. Thermodynamics: The laws of thermodynamics describe the essential role of energy and explain and predict the direction of changes in matter 6. Equilibrium: Any bond or intermolecular attraction that can be formed can be broken. These two processes are in a dynamic competition, sensitive to initial conditions and external perturbations.
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Learning Objectives NO2
1 (of 3) 1.02 The student is able to select and apply mathematical routines to mass data to identify or infer the composition of pure substances and/or mixtures? O N What is the EMPIRICAL formula of this molecule? Dinitrogen tetroxide is used as a rocket fuel in the titan rockets. What is the ratio of oxygen to nitrogen in the fuel tanks? 2:1 NO2
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Learning Objectives 2 (of 3) 1.03 Can you select and apply mathematical relationships to mass data in order to justify a claim regarding the identity and/or estimated purity of a substance? Sugar water Total cylinder -50.0 404.5 What is the temperature of this saturated sugar solution? (g.cylinder mass = 50.0g) Sugar Sugar water water sugar = 304.5 454.5g ~62oC
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Learning Objectives 3 (of 3) 1.14 The student is able to use data from mass spectrometry to identify the elements and the masses of individual atoms of a specific element. What is the [ ] of a solution with an absorption of 1.7 in the 230nm wavelength? ~ M
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