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Unit 2: Atomic Structure

Unit 2: Atomic Structure. Slide 1. Click Below for the Video Lectures. Atomic Models History of Atoms. Slide 2. Subatomic Particles. Slide 3. Subatomic Particles. Over the past century, scientists have discovered that the atom is composed of 3 subatomic particles: Protons Neutrons

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Unit 2: Atomic Structure

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  1. Unit 2: Atomic Structure Slide 1

  2. Click Below for the Video Lectures Atomic Models History of Atoms Slide 2

  3. Subatomic Particles Slide 3

  4. SubatomicParticles Over the past century, scientists have discovered that the atom is composed of 3 subatomic particles: Protons Neutrons Electrons

  5. Subatomic Particles Draw this diagram in your Cornell in your notes. Label all subatomic particles and include their charges!

  6. The Proton • Symbol = p+ • Relative Mass = 1 Atomic Mass Unit (AMU). • Actual mass = 1.674 x 10 -24 g • Location: Inside the nucleus 5. Electrical charge: Positive 6. Importance: The atomic number which is the identity of the element. 7. Discovered by: Ernest Rutherford in 1909

  7. The Electron • Symbol = e- • Relative Mass = 1 /1836 Atomic Mass Unit. 3. Actual mass = 9.11 x 10 -28 g 4. Location: Energy level outside the nucleus • 5. Electrical charge: Negative • Importance: The number of electrons located in the last energy level determine the chemical activity of the element. • Discovered by: J.J.Thomson in 1897

  8. The Neutron • Symbol = n • Relative Mass = 1 Atomic Mass Unit (AMU). • Actual mass = 1.675 x 10 -24 g 4. Location: Inside the nucleus 5. Electrical charge: Neutral 6. Importance: Is responsible for isotopes (atoms of the same element with different numbers of neutrons. 7. Discovered by: James Chadwick in 1932

  9. Atomic Number Atomic number (Z) of an element is the number of protons in the nucleus of each atom of that element.

  10. The Mass number (A) …is the number of protons and neutrons in the nucleus of an isotope. Mass Number Mass # = p+ + n0 8 18 18 8 75 75 33 Arsenic Phosphorus 31 16 15 Remember…Mass # = p+ + n0

  11. Isotopes …are atoms of the same element that differ in the number of neutrons. There mass is therefore different. Isotopes

  12. Ions • …are charged atoms where the number of electrons does not equal the number of protons • Cation – more protons then electrons • Anion – more electrons then protons

  13. HONORS ONLY** Atomic mass (Average atomic mass) …is the average of all the naturally occurring isotopes of that element. This is calculated using both the masses of each isotope and their percent abundances in nature. amu= atomic mass unit Atomic Masses Carbon = 12.011 AMU HONORS ONLY

  14. Electron Configuration!(4 types)

  15. 1. Shell Configuration:The Bohr Model Diagram • Shows how many electrons are found in each shell (principal energy level). • This is the configuration Niels Bohr would have come up with as the discoverer of the energy level!

  16. Shell Configuration (Bohr Diagrams) • Draw a nucleus with the element symbol inside. • Carbon is in the 2nd period, so it has two energy levels, or shells. • Draw the shells around the nucleus. C

  17. Shell Configuration (Bohr Diagrams) • Add the electrons. • Carbon has 6 electrons. • The first shell can only hold 2 electrons. C

  18. Shell Configuration (Bohr Diagrams) • Since you have 2 electrons already drawn, you need to add 4 more. • These go in the 2nd shell. • Add one at a time -starting on the right side and going counter clock-wise. C

  19. Shell Configuration (Bohr Diagrams) • Check your work. • You should have 6 total electrons for Carbon. • Only two electrons can fit in the 1st shell. • The 2nd shell can hold up to 8 electrons. • The 3rd shell can hold 18, but the elements in the first few periods only use 8 electrons. C

  20. 2. Sublevel Electron Configuration • Principal energy levels are made up of sublevels, much as a town is made up of streets. • The expanded configuration tells you how many electrons are found in each sublevel of each PEL. • Most of the time (and for all of the configurations you will be responsible for), one sublevel must fill up completely before the next one can get any electrons.

  21. s , orbital shapes

  22. p orbitals are peanut or dumbbell shaped.

  23. d orbitals

  24. f orbitals

  25. 8A 1A 1 2A 3A 4A 5A 6A 7A 2 3 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 4 s d p 5 6 7 f 6 7 group # = # valence (outside) e- Row = # shells

  26. 8A 1A 1 2A 3A 4A 5A 6A 7A 2 3 3B 4B 5B 6B 7B 8B 8B 8B 1B 2B 4 d 5 6 7 f 6 7 Subshells d and f are “special” group # = # valence e- 3d 4d 5d 6d 4f 5f

  27. Periodic table blocks

  28. Electron Configuration – “Spdf” HELIUM – 2 electrons 1s 2 Drawn as exponent group # # valence e- possibilities are: s: 1 or 2 p: 1-6 d: 1-10 f: 1-14 Total e- should equal Atomic # row # shell # possibilities are 1-7 7 rows Lowercase s subshell possibilities are s, p, d, or f 4 subshells

  29. 3. Orbital Box Diagram • Shows how many electrons are in each ORBITAL of each sublevel, and what each electron’s SPIN is. • Orbitals are all the same size, they can all fit up to two electrons in them. • The spin of electrons is indicated by arrows up and down. • If the orbital has two electrons in it, the first will have an up spin, and the second will have a down spin. • The number of arrows will equal the number of electrons in the sublevel.

  30. Guide to Drawing Orbital Diagrams

  31. Drawing an Orbital Diagram Draw the orbital diagram for nitrogen. Step 1 Draw boxes to represent the occupied orbitals. Nitrogen has an atomic number of seven, which means it has seven electrons. Draw boxes to represent the 1s, 2s, and 2p orbitals.

  32. Drawing Orbital Diagram Step 2 Place a pair of electrons in the last occupied sublevel in separate orbitals. We place the remaining three electrons in the 2s orbitals.

  33. Drawing Orbital Diagram Step 3 Place remaining electrons with opposite spins in each filled orbital. First we place a pair of electrons with opposite spins in the 2p orbitals, with arrows in the same direction.

  34. Click Below for the Video Lectures Electron Configuration

  35. 4. Electron (Lewis) Dot Diagram • VALENCE ELECTRONS • Are the electrons in the outermost shell (furthest energy level from the nucleus), which is also called the valence shell. • The number of valence electrons that an atom has can be determined by the last number in the basic electron configuration. The number of valence electrons that an atom has determines its physical and chemical properties!

  36. The Electron (Lewis) Dot diagram Nitrogen has 5 valence electrons. 1) First we write the symbol. N 2) Then add 1 electron at a time to each side. 3) Until they are forced to pair up.

  37. Group 1 (alkali metals) have 1 valence electron

  38. Group 2 (alkaline earth metals) have 2 valence electrons

  39. Group 13 elements have 3 valence electrons

  40. Group 14 elements have 4 valence electrons

  41. Group 15 elements have 5 valence electrons

  42. Group 16 elements have 6 valence electrons

  43. Group 17 (halogens) have 7 valence electrons

  44. Group 18 (Noble gases) have 8 valence electrons, except helium, which has only 2

  45. Transition metals (“d” block) have 1 or 2 valence electrons

  46. Lanthanides and actinides (“f” block) have 1 or 2 valence electrons

  47. Checking for understanding

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