1 / 12

Chapter 18

Chapter 18. Atomic Models. Viewing the Atom. The atom is difficult to view because it is smaller than a wave of visible light The number of atoms in one baseball would be like counting the number of ping pong balls it would take to fill a sphere the size of the Earth

janus
Download Presentation

Chapter 18

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Chapter 18 Atomic Models Presented by April Senger

  2. Viewing the Atom • The atom is difficult to view because it is smaller than a wave of visible light • The number of atoms in one baseball would be like counting the number of ping pong balls it would take to fill a sphere the size of the Earth • The Scanning Tunneling Microscope allows us to “see” atoms indirectly by dragging a tiny needle across the surface and using a computer to create a topographical image • This is called nanotechnology Presented by April Senger

  3. Models • Physical models are for small, large, slowly occurring, or quick observations • The atom is best represented by a conceptual model • Conceptual models look at the whole system • The economy, population growth, the spread of disease, and team sports are also best represented with conceptual models Presented by April Senger

  4. Concept Check • A basketball coach describes a playing strategy to her team by way of sketches on a game card. Do the illustrations represent a physical or conceptual model? • Conceptual Presented by April Senger

  5. Spectroscopes & Atomic Spectrum • The electrons are represented in the atomic model by shells or energy levels • Every atom has a distinct number or shells and electrons and can absorb energy differently • When the energy absorbed by an atom is released, it gives off a specific atomic spectrum • We can use a spectroscope through diffraction to split the colors of the rainbow out like a prism • Each atom has its own rainbow fingerprint Presented by April Senger

  6. Concept Check • How might you tell what elements are in a star? • A spectroscope can analyze their spectral patterns and identify their fingerprints • We tried this with our own sun in the 1800’s and found Hydrogen (already identified) and another we named Helios after the Greek word for sun-common name Helium Presented by April Senger

  7. Historical Outline • Democritus was a Greek philosopher that theorized that everything was made of atoms but there was no evidence. • John Dalton said that atoms were indestructible spheres of solid matter (the billiard ball model). They can be joined together to form molecules. He had evidence. • In 1913, Niels Bohr decided that the atom was like a solar system where the planets were the electrons and the sun was the nucleus. Presented by April Senger

  8. More History • Each electron has its own specific energy and that determines what path it can take around the nucleus. These are called energy levels. • Electrons behave like waves and particles so Bohr’s theory didn’t work • We developed the Modern Atomic Theory that says that electrons are not like planets. Electrons are more like vibrating strings. • Electrons are hard to find…Think of a spinning fan and each individual blade. It is impossible to measure both an electron’s speed/direction and location Presented by April Senger

  9. The light released is called a photon and a quantum is the smallest unit of light The quantum hypothesis states that a steady stream of light is actually a continuous stream of tiny packets of light Bohr used the amount of light released to determine the energy levels of an atom He stated that the lowest level is n = 1, then 2, 3 and so on This model started to look like the solar system so it is thus named the Planetary Model The light emitted by atoms was equal to the energy it would take to jump between levels Bohr Presented by April Senger

  10. Shells • Shells are a region of space about the atomic nucleus within which electrons may reside • Each shell holds a different number of electrons • The shells hold the following number electrons from level 1 up 2, 8, 8, 18, 18, & 32 • The electrons that are in the outermost level are the ones that determine an atoms ability to chemically react • We call these electrons Valance Electrons Presented by April Senger

  11. Valance Electrons & Their Patterns • Group 1 has one valance • Group 2 has two • Group 13 has 3 • Group 14 has 4 • Group 15 has 5 • Group 16 has 6 • Group 17 has 7 • Group 18 has 8 • The rest of the elements vary and some have more than one possible number of valance electrons Presented by April Senger

  12. Shell Model • We know that the shell model is not the most accurate • It is the easiest for us to draw without the aid of a computer • Mostly, we use concentric circles such as those found on page 318 • The outer most electrons will be useful in drawing Lewis Dot Structures Presented by April Senger

More Related