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Atomic Models

Atomic Models. fire. Democritus. earth. air. water. Aristotle. Early Greek Theories. 350 B.C - Aristotle Theory that matter was made of four “elements”: earth, fire, water, air. 400 B.C. - Democritus thought matter could not be divided indefinitely.

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Atomic Models

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  1. Atomic Models

  2. fire Democritus earth air water Aristotle Early Greek Theories • 350 B.C - Aristotle • Theory that matter was made of four “elements”: earth, fire, water, air. • 400 B.C. - Democritus thought matter could not be divided indefinitely. • Aristotle was wrong. However, his theory persisted for 2000 years. • This led to the idea of atoms.

  3. John Dalton • 1800’s • Proposed an Atomic Theory which states; • All matter is made of atoms. • Atoms of an element are identical. • Each element has different atoms. • Atoms of different elements combine in constant ratios to form compounds. • Atoms are rearranged in reactions. Jelly beans

  4. The Electron • Late 1800’s • J. J. Thomson • A gas beam was repelled away by a magnet. • The gas is made of atoms, so…. • atoms must contain CHARGED particles! Magnet The beam wad repelled (away)

  5. Thomson’s atomic model • Thomson found that there were small electrons embedded in the atom like chocolate chips in a chocolate chip cookie. • Atoms are solid spheres made-up of a solid positive mass (cookie) with tiny negative particles embedded in the positive core Negative electrons Positively charged cookie.

  6. Rutherford & the Nucleus • 1908 • Discovered by his famous ‘gold foil’ experiment. • He shot positively charged particles at a very thin piece of gold foil. • He expected the particles to go right through. Most did go through or got deflected. • But a few BOUNCED BACK! • THEY HIT SOMETHING SOLID!

  7. Rutherford’s gold foil experiment • This proved that: • the atom had a dense but very small positive core • the electrons were far away from the nucleus • Most of the atom is just EMPTY SPACE!

  8. That would be like a basketball (nucleus) on the 50 yard line, and you were an electron in a seat way up in the stands.

  9. Neils Bohr • Early 1900’s • Electrons move in orbits, energy levels • Electrons in Definite energy Levels around  the nucleus • Electrons can move to different energy levels if they gain or lose energy.

  10. Quantum Mechanical Modelor Electron Cloud Model • Electrons move around the nucleus very fast. • You can’t predict where an electron will be at any moment. • The analogy here is that of a "beehive" where the bees are the • electrons and they ‘buzz’ around the nucleus.   

  11. Atoms and elements

  12. Atomic Structure

  13. Matter…. • Is Everything! • It’s the amount of mass in an object • Measured in kilograms • It has volume: takes up space • Measured in milliliters or cubic centimeters • All matter is composed of elements • 88 natural elements

  14. Elements are… • Purest of the pure substances • There are 112 of them known so far • They are organized on the Periodic Table • The most common elements: 1. oxygen. ( air, water, rock, living things) 2. Hydrogen (water, living things, sun, stars) 3. Nitrogen (air 80%, living things, soil) • 4. magnesium, iron, aluminum, carbon

  15. Every element on the periodic table is assigned a box with specific information in it.

  16. Atomic Symbol • 1 or two letter symbol • First letter is always CAPITOL, second letter always lower case. Co (cobalt) is not same as CO (carbon monoxide) • Examples: • C for carbon • Ca for calcium • Cl for chlorine • Cf for californium CF C F Cf Not correct!!!

  17. Atoms • Smallest part of an element. • Too small to be seen. • All atoms are made of the same basic ‘ingredients’ • Atoms vary in size and mass. • Atoms are made up of: • Protons (+ charge) • Electrons (-charge) • Neutrons (neutral)

  18. Proton • Dense, positively charged particle • There are equal # of protons and electrons in a neutral atom. • Proton’s mass = 1 amu • Proton # is their Atomic number. Ex: 6 protons is element 6 or carbon + = -

  19. Neutron • Difficult to ‘find’ because they have no charge • Same mass as a proton (1 amu), but has NO CHARGE (neutral) • Neutrons are in the nucleus. No charge

  20. Neutral atoms • Since protons are positively charged • And electrons are negatively charged, • A neutral atom has EQUAL # protons and electrons! = Ex: chlorine 17 protons 17 electrons + -

  21. Mass Number • Mass Number = # protons + # neutrons in nucleus • Protons and neutrons make up the mass of the nucleus (and 99.9% of the atom’s mass) • Ex: Chlorine’s mass number is 35 17 protons and 18 neutron = 35

  22. Number of neutrons Mass number of oxygen 16 atomic number (protons) -8 number of neutrons 8 Mass number of uranium 238 atomic number (protons) -92 number of neutrons 146 * The number of neutrons in an atom can vary.

  23. There are two forms of carbon… Carbon- 14 has 6 protons +8 neutrons ________________ Total mass = 14 Carbon-12 has 6 protons +6 neutrons Total mass = 12 Carbon-12 and Carbon-14 are Isotopes. So… what is an isotope?

  24. Isotope • Atoms of the same element with a different number of neutrons • So… • Same # of Protons • Different # neutrons • Different mass number

  25. Periodic Table of Elements

  26. Dmitri Mendeleev • First Table made by arranging the 63 known elements in order of • atomic weight • grouping them by similarity of properties. • Predicted • the existence of new elements • pointed out that some of the known atomic weights were wrong • He left space on his table for new elements, and predicted yet-to-be-discovered elements

  27. Aren’t you glad it doesn’t look like this now? This gives me a headache. Gaps where he knew that missing elements should be.

  28. The Modern Periodic Table • What season comes after our current season? After that? • The periodic tables has: • Horizontal Rows (label these from top to bottom #’s 1 through 7. The row number corresponds to how many energy levels the atom in that row have.) • These rows show TRENDS! • For example, as you move across a row, elements go from metallic to less metallic. • When you finish a row, the next row repeats those properties. Just like the seasons repeat themselves year after year.

  29. MORE about the P.T. ! • What are some things you have in common with your family? • The periodic table also has COLUMNS. They are called: • Groups or Families– • Elements in the same grouphave similar physical and chemical properties http://www.youtube.com/watch?v=f3p8paK24ac

  30. More about Groups on the P.T. • The groups can be labeled 1 through 18 (most modern way) • or 1A, 1B, 3B, 4B, etc. (old-fashioned) • Groups with an A have a “little of everything” metal, non-metal, reactive, non-reactive • Groups with a B are “transition metals” and pretty much alike.

  31. Metalloids Hey! Label your table! H 1 He 2 1 Li 3 Be 4 B 5 C 6 N 7 O 8 F 9 Ne 10 Nonmetals 2 Na 11 Mg 12 Al 13 Si 14 P 15 S 16 Cl 17 Ar 18 3 K 19 Ca 20 Sc 21 Ti 22 V 23 Cr 24 Mn 25 Fe 26 Co 27 Ni 28 Cu 29 Zn 30 Ga 31 Ge 32 As 33 Se 34 Br 35 Kr 36 4 METALS Rb 37 Sr 38 Y 39 Zr 40 Nb 41 Mo 42 Tc 43 Ru 44 Rh 45 Pd 46 Ag 47 Cd 48 In 49 Sn 50 Sb 51 Te 52 I 53 Xe 54 5 Cs 55 Ba 56 Hf 72 Ta 73 W 74 Re 75 Os 76 Ir 77 Pt 78 Au 79 Hg 80 Tl 81 Pb 82 Bi 83 Po 84 At 85 Rn 86 6 Fr 87 Ra 88 Rf 104 Db 105 Sg 106 Bh 107 Hs 108 Mt 109 7 La 57 Ce 58 Pr 59 Nd 60 Pm 61 Sm 62 Eu 63 Gd 64 Tb 65 Dy 66 Ho 67 Er 68 Tm 69 Yb 70 Lu 71 Ac 89 Th 90 Pa 91 U 92 Np 93 Pu 94 Am 95 Cm 96 Bk 97 Cf 98 Es 99 Fm 100 Md 101 No 102 Lr 103

  32. And color code, too!Come get three colored pencils but you don’t’ have to use these offensive colors. 1 Nonmetals 2 3 4 Metals 5 6 7 Metalloids Zumdahl, Zumdahl, DeCoste, World of Chemistry2002, page 349

  33. Properties of Metals, Nonmetals, and Metalloids METALS malleable, lustrous, ductile, good conductors of heat and electricity NONMETALS gases or brittle solids at room temperature, poor conductors of heat and electricity (insulators) METALLOIDS (Semi-metals) dull, brittle, semi-conductors (used in computer chips)

  34. Periodic Trends • Wow! Can’t you just wait? • The periodic table shows all sorts of trends, but we will keep it very basic.

  35. Atomic size(radius) • The size of the atom increases as you go down the table. • Size decreases as you go across.

  36. Electronegativity -  the tendency of an atom to attract electrons

  37. Ionization Energy -  the amount of energy required to remove an electron from the atom or molecule

  38. Electron Affinity -  the amount of energy released when an electron is added to a neutral atom or molecule to form a negative ion.

  39. Melting/Boiling Point • Highest in the middle of a period.

  40. The elements get more metallic as you go down the table, and less metallic as you go across.

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