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Chapter 3 – Atomic Structure

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1 Chapter 3 – Atomic Structure
Atom - Greek for “Atomon” means“Indivisible” - Smallest unit that can exist alone or in combination with other atoms. Two main areas of the atom: Nucleus ____________________________ - ____________________________ Electron cloud - __________________________________ - __________________________________ Atom itself is neutral: Why? Number of p+ = e- n0 are neutral - no effect

2 What if you change the number of neutrons? electrons?

3 More on Structure of an Atom … Things we know…
Compare size of electron cloud to nucleus _____________________________________________________________________________ Nucleus “marble” How much smaller????? Nucleus is a marble in the middle of a football stadium. Electron Cloud “football field”

4 Compare size of proton, neutron, and electron
Interesting Stuff … all the mass of the atom is in the nucleus…Wow! What does that mean about the density of the nucleus? Electron’s mass = __________ Nucleus Proton’s mass = __________ Electron Cloud Neutron’s mass = __________ 1 amu (atomic mass unit) = _________________ The atomic mass unit is easier to use to describe something so ridiculously small! g

5 Does an electron having “0” amu means it weighs nothing?
Not Exactly … It’s just it is so small it does not matter relatively …

6 Easier to say 10 tons than 20,000 lbs.
A word about the … amu __________________________________________________ Similar to: 2000 lbs. = 1 ton Easier to say 10 tons than 20,000 lbs. Just like: 1 amu (atomic mass unit) = x g Easier to say 2 amu than x g

7 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... A Little Bit of History Before I start into the history… …a little bit about Indirect Evidence??? Where to hunt? Measure thickness of paper or a dollar?

8 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... A Little Bit of History 400 BC Democritus The idea of the atom stems back to 400 BC by a Greek thinker named Democritus …he called matter “atomon” meaning “indivisible”

9 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... Click black box for video A Little Bit of History 1782 Antoine Lavoisier Law of conservation of mass _________________________________________________________________________

10 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... H2O A Little Bit of History two H’s one O For this compound to be water… it must have exactly 2 H and 1 O What is this? H2O2 1799 Joseph Proust Law of definite proportions _____________________________________________________________________________________________________________________________

11 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... Carbon monoxide CO C = 12 g O = 16 g Carbon dioxide CO2 C = 12 g O = 32 g A Little Bit of History Ratio : 1 1803 Ratio : 2 Same elements but different ratios make different compounds John Dalton Law of multiple proportions _____________________________________________________________________________________________________________________________

12 How about... A Little Bit of History The Atomic Theory
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... A Little Bit of History 1803 John Dalton The Atomic Theory _____________________________________________________. Atoms of the same element are chemically alike. Atoms of different elements are chemically different. Atoms combine in whole # ratios to form compounds. ___________________________________________________________________________________________________________.

13 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... Click black box for video A Little Bit of History Joseph Thompson Used a cathod ray tube to prove there were negative charged particles (now known as electrons) in an atom. This opened the way to the idea that an atom was not just a solid sphere not able to be broken down anymore. 1897

14 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... A Little Bit of History Robert A. Millikan Proved that the e- is really small (“0 amu”)…not really…he showed that the _______________________________________________________________________________________________. 1909

15 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... A Little Bit of History Earnest Rutherford 1911 ______________________________, he proved that the electron cloud was huge in volume comparison to the nucleus and the nucleus was extremely dense.

16 How about... A Little Bit of History
How did we figure out all this stuff about the atom??? Because the atom is so small !!!!! How about... A Little Bit of History Neils Bohr 1913 _________________________________________________________________________________________________________________________________________________________.

17 The Evolving Atomic Model Summary
Dalton Model 1803 – John Dalton believed that an atom was an indestructible particle with no internal frame. (Billiard Ball Model) Thomson Model 1897 – J.J. Thomson discovers the electron. He believed electrons were embedded in positive charge sphere. (Plum pudding Model) Rutherford Model 1911 – Ernest Rutherford discovers that there is a dense, positively charged nucleus. Electrons go around the nucleus. Bohr Model 1913 – Niels Bohr enhances Rutherford’s model by having electrons move in a circular orbit at fixed distances from the nucleus.

18 Atomic Number – ______________________________________________________________________________________________________________ Mass Number – ______________________________________________________________________________________________________________ Atomic Weight 32.065 Shorthand method: 32 S 16 Mass # (rounded) 32 Atomic # (# of p+ or e-)- Mass # - Atomic # = n0

19 Atomic Weight – ______________________________________________________________________________________________________________ Atomic Weight 32.065 Shorthand method: 32 S 16 Mass # (rounded) 32 Atomic # (# of p+ or e-)- Mass # - Atomic # = n0

20 Atomic Weight = (Avg. mass of isotopes) = 32.066
Atomic # = (number of protons or electrons) = 16 Mass # = (Atomic weight rounded) = 32 # p+ = (same as Atomic #) = 16 p+ # e - = (same as Atomic #) = 16 e - # n0 = (Mass # - Atomic #) = 16 n0 (32 – 16) Try Sodium (Na): Atomic Weight = (Avg. mass of isotopes) = ________ Atomic # = (number of protons) = ________ Mass # = (Atomic weight rounded) = ________ # p+ = (same as Atomic #) = ________ # e - = (same as Atomic #) = ________ # n0 = (Mass # - Atomic #) = ________

21 PRACTICE THESE………… Au Ag Pb Atomic Weight = (Avg. mass of isotopes) = _______________ Atomic # = (number of protons) = ______________ Mass # = (Atomic weight rounded) = ______________ # p+ = (same as Atomic #) = ______________ # e - = (same as Atomic #) = ______________ # n0 = (Mass # - Atomic #) = ______________

22 Isotopes Ex. H has 3 isotopes H H H
– atoms of the same element with different masses due to a different number of n0 Ex. H has 3 isotopes 1 2 3 H H H 1 1 1 ________________________________________________…so it is still hydrogen and acts like hydrogen but it is a little heavier with each additional neutron added…

23 8 Carbon –12 Carbon - 14 Different number of neutrons
If you change the number of neutrons…it is still Carbon but it makes a different isotope. Carbon – Carbon - 14 Different number of neutrons 8

24 1 mole = _____________________
Like hydrogen H NOT --- Even though he is cute! H H O 1 mole = ________________________ Like water

25 You need this many atoms to even see them because they are so small
How do I know how much exactly one mole is? The periodic table… 1 mole = ______g Periodic Table 1 mole of Iron = g 1 mole of Zinc = g 1 mole of copper = g

26 Moles Mole: the amount of a substance that contains as many particles as there are atoms in exactly 12g of carbon-12.

27 Moles Avogadro’s Number: the number of particles in exactly one mole of a pure substance ~ x 1023 (we’ll use 6.02 x 1023)

28 Moles 602,200,000,000,000,000,000,000 If you had x 1023 pennies and gave away 1 million a day to every person on earth, it would take you 3000 years to distribute all your money!! 3-30

29 Molar Mass Molar Mass: the mass of one mole of a pure substance.
~ the mass of single atoms or molecules is measured in amu’s. The mass of a mole of the same substance is numerically the same, with the units g/mol. Ex. H20 = H x 2 = 1.01 x 2 = + O x 1 = x 1 = 18.02g/mol 3-31

30 Molar Mass 1) What is the molar mass of BaCl2?
2) What is the molar mass of NaI?

31 Molar Mass This photograph shows one mole of solid (NaCl 58.44g/mol), liquid (H2O g/mol), and gas (N g/mol). 3-33

32 Mass/Mole Conversions
When given the number of moles, you can find the grams by: Moles _g__ = grams 1 mole Ex moles of H2O = X g

33 Mass/Mole Conversions
Moles _g_ = grams 1 mol Now try these problems: 3) moles of BaCl2 equals how many grams? 4) moles of SO2 equals how many grams? 3-35

34 Mass/Mole Conversions
When given the amount in grams, you can calculate the number of moles by: g 1 mol = moles g Ex g NaCl = X moles

35 Mass/Mole Conversions
g 1 mol = moles g Now try these problems: 5) g of NaCl equals how many moles? 6) g of ammonia (NH3) equals how many moles? 3-39

36 Mass/Mole Conversions

37 Particle/Mole Conversions
You can also calculate between moles and number of particles: (1.0 moles = 6.02 x 1023 particles) To enter this number into your calculator, punch in 6.02 EE button (one time) 23. 3-41

38 Particle/Mole Conversions
Ex moles of marble (CaCO3) contains how many molecules? *Particles can be molecules or atoms 7) How many molecules are in 5.0 moles of carbon dioxide?

39 Particle/Mass Conversions
Ex. What is the mass of 3.25 x1023 molecules of N2? 8) How many molecules are g of NaCl?

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