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# Ch 2 Atoms/Molecules

Ch 2 Atoms/Molecules. Basic structure. John Daltons-Atomic theory JJ Thomson/Crookes-Cathode Ray Tube Experiments &amp; Plum pudding model Rutherford-Gold Foil Experiment Millikin’s Oil Drop Experiment. Protons mass = 1 amu charge +1 Neutrons mass = 1 amu charge 0

## Ch 2 Atoms/Molecules

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1. Ch 2 Atoms/Molecules

2. Basic structure • John Daltons-Atomic theory • JJ Thomson/Crookes-Cathode Ray Tube Experiments & Plum pudding model • Rutherford-Gold Foil Experiment • Millikin’s Oil Drop Experiment

3. Protons mass = 1 amu charge +1 • Neutrons mass = 1 amu charge 0 • Electrons mass = negligible charge -1 • Amu = atomic mass unit. • 1 amu = _____________ grams

4. Txt pg Protons mass = 1. 0073 amu charge = +1.69 x 10- 19Coulumbs (+1 Charge) Nuetrons mass = 1.0087 amu charge = 0 Coulumbs Electrons mass = 0.0005486 amu charge = -1.69 x 10- 19Coulumbs (-1 Charge) 1.0073 amu 1.0087 amu 0.00005486 amu

5. Atomic mass vs Atomic Weight • Atomic mass = mass of an individual atom • Atomic Weight = average mass of all the isotopes (Carbons atomic wt. = 12.011) Carbon -12 12C Carbon -14 14C 6 protons 6 protons 6 neutrons 8 neutrons 6 electrons 6 electrons

6. Isotopes • Same element, different mass (due to differing amts. of neutrons) • Stable elements #Protons (p) = #Neutrons(n) • Radioisotopes are the unstable form of the element due to having a larger number of neutrons than protons

7. Isotope symbols • Uranium -236 236 U We can always assume that a atom is neutral unless noted Atomic number tells us the protons (92). This is many times left off the symbol because it will always be 92 if the element is U. We assume then that there must be 92 e- The mass number tells us the # neutrons.

8. Mass Spec • Relative Abundance.

9. Average atomic weight • Takes the most stable isotopes and their relative abundance to calculate the averages

10. Ions • Atoms whose electrons do not equal the protons. Metals = cations (+ ions) Nonmetals = anions ( - ions) Opposites attract to form ionic cpds (very strong bond=almost always solids with high melting pts) Fe +3 and Cl-1

11. Predicting formulas • Review: The atoms always combine so that the number of + balances the number of – charges. • Criss Cross method

12. Polyatomic ions • Groups of atoms with a charge • Treat as a single unit. • Place ( ) around it if you have more than l Ca + 2 and NO3 -1

13. Naming Ionic • First name is the name of the element written first (cation) unless it’s the Group NH4+1 (ammonium) • Last name is the name of the element written last with an ide ending unless it’s a group (then use the group name) • NaCl NaNO3 • CaBr Ca(IO3) • Ag2S Ag CN

14. Middle names • Ionic cpds that have a metal with more than one charge/oxidation state need middle names (mainly transitional elements) • Fe+2 and Fe +3 • Cu +1 and Cu +2 • Pb +2 and Pb +4 • Sn +2 and Sn +4 • Hg +1 (Hg2+2) and Hg +2

15. Name the following ionic cpds • FeCl3 • PbS • CuBr • Cu Br2 • Sn (CN)4

16. Molecular cpds • These are primarily nonmetals elements attached to nonmetal elements due to the sharing of their valence electrons (Also called covalent cpds) • Which of the following are ionic (metal/non) and which are molecular (non/nonmetal) • CaBr2 AgF SO2 LiNO3 • IF5 CCl4 Cl2 BI3

17. Naming molecular cpds • First name is the name of the element written first • Last name is the name of the element written last with an ide ending • Sulfur= sulfide chlorine = chloride • Oxygen = oxide iodine = iodide • Both names have a prefix indicating the number of each atom

18. Prefixes used on molecular cpds • Mono =1 • Di =2 • Tri =3 • Tetra =4 • Penta =5 • Hexa =6 • Hepta=7 • Octa=8 • Nano =9 • Deca =10

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