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Physics 102-002 Announcements

Physics 102-002 Announcements. WebAssign – Chapter 10 due next Tuesday Chapter 11 due next Wednesday Exam #2 corrections due today Revised class schedule posted on website.

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Physics 102-002 Announcements

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  1. Physics 102-002Announcements • WebAssign – • Chapter 10 due next Tuesday • Chapter 11 due next Wednesday • Exam #2 corrections due today • Revised class schedule posted on website 90x80 nm STM image of a GaAs nanowire sliced through the face and imaged with atomic resolution. The wire diameter is ~50 nanometer, this particular (and special) nanowire consists of two individual nanocrystallites perfectly fused together in the middle. In the top-left corner the inset shows a 10x10 nm zoom-in on the center of the wire showing the individual As inside the wire – on the inset one can see the perfect (atom-by-atom) junction of two nanocrystallites inside the wire. Images were recorded in constant current mode at –2.0V and 0.2nA.

  2. Class Schedule

  3. Chapter 11The Atomic Nature of Matter • The Atomic Hypothesis • Characteristics of Atoms • Atomic Imagery • Atomic Structure • The Elements • The Periodic Table of the Elements • Compounds and Mixtures • Molecules

  4. The Atomic Hypothesis • All things are made of atoms • Atoms are little particles that move around in perpetual motion • Atoms attract each other when they are more than about • 10-10 m = 0.1 nm = 1 Å apart • Atoms repel on being squeezed together Brownian motion simulation http://www.geocities.com/piratord/browni/Difus.html Physics Place videos

  5. Question 1 Why does air spread out to fill a room? a) The molecules repel each other so the air expands to fill up the available space b) The molecules move randomly, and end up all over the place c) The energy of the system is lowered when the air fills the entire room

  6. Question 1 Answer Why does air spread out to fill a room? a) The molecules repel each other so the air expands to fill up the available space b) The molecules move randomly, and end up all over the place c) The energy of the system is lowered when the air fills the entire room 

  7. Characteristics of Atoms Atoms are REALLY tiny Atoms move around Thermal movement of atoms simulation http://nic.sav.sk/fyzikraj/MovingDiscs/MovingDiscs.html A cylindrical block of lithium with diameter and height of 2.4 cm contains approximately 1023 Li atoms. Atoms are REALLY numerous Atoms are ageless Atoms you breathe have been around since the beginning of time, but have combined/recombined many times. Some have undergone fusion or fission.

  8. Atomic Imagery This picture is in the book. The barriers were assembled by individually positioning Fe adatoms using the tip of a low temperature scanning tunneling microscope (STM). A circular corral of radius 71.3 Angstrom was constructed in this way out of 48 Fe adatoms. Cyclopentene on single-domain Si Atomic-force-microscope cross-sectional image of a carbon nanotube ring that is bridging two gold electrodes. Scanning Tunneling Microscopy: How it’s done and more images.

  9. Atomic Structure Atoms are built from: electrons  , protons  and neutrons  Mn=1 Me=1/2000 Mp=1 Mass (in amu) A neutron walked into a bar and asked how much for a drink.  The bartender replied,  "for you, no charge."  No charge Electrical Charge + - A Hydrogen Atom (Using the “shell model”)        Hydrogen (more accurately): a proton surrounded by an electron cloud A Helium Atom nucleus

  10. The Elements Atoms cannot be divided using chemicals. They do consist of parts, which include protons, neutrons, and electrons, but an atom is a basic chemical building block of matter. Almost all of the mass of an atom is in its nucleus; almost all of the volume of an atom is occupied by electrons. The number of protons (also known as its atomic number) determines the element. Varying the number of neutrons results in isotopes. Varying the number of electrons results in ions. Isotopes and ions of an atom with a constant number of protons are all variations of a single element. Elements are substances composed of atoms of the same kind. There are more than 112 currently known elements. Each has specific physical characteristics. Atomic structure animation table for the first 11 elements of the Periodic Table

  11. The Periodic Table Link to the periodic table above.

  12. Compounds, Mixtures, and Molecules Compound: A pure chemical material that consists of more than one kind of atom. Examples: water; PVC; table sugar (sucrose); table salt (sodium chloride) Molecule: 2 or more atoms held together by the sharing of electrons. A compound is a collection of 2 or more molecules of the same kind (like an element is a collection of 2 or more of the same kind of atom). Mixture: A collection of 2 or more different types of atoms or molecules that don’t chemically bond with each other. Examples: air (a mixture of nitrogen, oxygen, and other gases); gunpowder (charcoal, sulfur, and potassium nitrate ) Methane Gas Water

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