Lecture 01- Atomic Structure
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The document provides an overview of atomic structure, detailing foundational theories by Democritus, Dalton, Thomson, Rutherford, and Bohr. It explains the composition of atoms, subatomic particles, and the behaviors of electrons, as well as categorizing materials into conductors, insulators, and semiconductors based on electron stability. The lecture emphasizes the significance of atomic structure in determining the properties of matter.
Lecture 01- Atomic Structure
- 1. Duration: 60 min DPT Medical Physics Lecture 01 Structure of Atom Instructor: Engr. Taimoor Muzaffar Gondal [email protected] Lecture 01
- 2. Duration: 60 min DPT Medical Physics Lecture 01 Atomic Structure All matter is composed of atoms. Understanding the structure of atoms is critical to understanding the properties of matter
- 3. Duration: 60 min DPT Medical Physics Lecture 01 History of Atom A Greek philosopher who was the first person to use the term atom. He thought that if you take a piece of matter and divide it and continue to divide it you will eventually come to a point where you could not divide it any more. This fundamental or basic unit was what Democritus called an Theory of the universe: 1. All matter consists of atoms, which are bits of matter too small to be seen. 2. There is an empty space between atoms and Atoms are completely solid. 3. Atoms have no internal structure 4. Each atom (of a different substance) is different in size, weight and shape. Democritus
- 4. Duration: 60 min DPT Medical Physics Lecture 01 1. All matter consists of tiny particles called atoms. 2. Atoms are indestructible and unchangeable. 3. Elements are characterized by the weight of their atoms. 4. When elements react, it is their atoms that have combined to form new compounds. John Dalton
- 5. Duration: 60 min DPT Medical Physics Lecture 01 J.J. Thomson Discovered Electron using Cathode Ray Tube. A vacuum tube, charge is passed through it. To see the charge a fluorescent screen is placed, charge will left a dot. Two oppositely charged deflecting coils are used.
- 6. Duration: 60 min DPT Medical Physics Lecture 01 This beam will always travel straight if not interfered he deflection coils each have a specific charge. One is positive and the other is negative. Thomson showed (as in the diagram above) that the charge would deflect away from the negative coil. He then stated that this charge was thus a negative charge He did not predict the movement of these electrons. He predicted the mass of Electron and earned Nobel Prize in Physics. Contd.
- 7. Duration: 60 min DPT Medical Physics Lecture 01 Ernest Rutherford Gold Foil Experiment: He fired alpha particles (positively charged) at a gold foil. He measured the deflection as the particles came out the other side. Most of the particles did not deflect at all. But a fewer particles deflected in various direction. He said that there must be a positive center of the foil. He called this center the nucleus.
- 8. Duration: 60 min DPT Medical Physics Lecture 01 atomic radius ~ 100 pm = 1 x 10-10 m nuclear radius ~ 5 x 10-3 pm = 5 x 10-15 m
- 9. Duration: 60 min DPT Medical Physics Lecture 01 Neil Bohr Using his knowledge of energy and quantum physics he was able to perfect Rutherford’s model. He was able to answer why the electrons did not collapse into the nucleus. Electron orbit the nucleus in orbits that have a set size and energy. The lower the energy of the electron, the lower the orbit. This means that as electrons fill up the orbitals, they will fill the lower energy level first. If that energy level is filled, a new energy level will begin. Radiation is when an electron moves from one level to another. Results
- 10. Duration: 60 min DPT Medical Physics Lecture 01
- 11. Duration: 60 min DPT Medical Physics Lecture 01 1. The smallest part of an element is called an atom. 2. Each atom (of an element) is different in structure from other atomsAn atom can be divided in smaller subatomic particles: Protons, Electrons and Neutrons 3. The nucleus is the center of an atom. 4. It contains protons and neutrons. 5. Electrons orbit the nucleus 6. As we go up the periodic table, an electron and proton is added. Electrons occupy a certain energy level (of a certain size) 7. Once the energy level is full, a new level begins 8. Within each of these levels are specials types of orbitals. 9. These depend on the energy level Each orbital can contain two electron Summary of Atomic Structure
- 12. Duration: 60 min DPT Medical Physics Lecture 01 Conductors, Insulators and Semiconductor The stability of the electrons in the outer ring determines whether a material made from this element is a conductor, insulator, or semiconductor. Elements whose electrons are unstable and can easily move from one atom to another make good conductors. Elements whose electrons are stable and can not easily move from one atom to another make good insulators. Any elements that are not considered conductors or insulators are categorized as semiconductors.
- 13. Duration: 60 min DPT Medical Physics Lecture 01 When an element’s outer electron ring is incomplete or not full, its electrons can move more freely from one atom to another atom. Elements whose electrons can move more freely make good conductors. In general, most metals make good conductors because they only have one or two electrons in their outer band. Silver and gold are the best conductors. Copper is the second best conductor. Most wiring uses copper wire because it is a good conductor and is less expensive than the other metals. Conductors
- 14. Duration: 60 min DPT Medical Physics Lecture 01 • When an element’s outer ring is complete, or full, its electrons can not easily move from one atom to another atom. • Elements whose electrons can not move freely make good insulators. • Examples of good insulators are glass, plastic, rubber, paper, or air. Most wiring uses plastic as an insulator. • Plastics are polymers or long chains of atoms bonded to one another. Viewing the atomic structure of plastics is far beyond the scope of this class (If you are interested in such topics, you may want to take AP Chemistry.). • Neon and argon, both gases, are good insulators and are often used in light bulbs. Insulators
- 15. Duration: 60 min DPT Medical Physics Lecture 01 • When an element’s outer ring is neither complete nor incomplete, the element is considered to be a semiconductor. • Examples of good semiconductor materials are • Carbon (used to make resistors) • Silicon (used to make transistors) Semi Conductors
- 16. Duration: 60 min DPT Medical Physics Lecture 01 • When an element’s outer ring is complete, or full, its electrons can not easily move from one atom to another atom. • Elements whose electrons can not move freely make good insulators. • Examples of good insulators are glass, plastic, rubber, paper, or air. Most wiring uses plastic as an insulator. • Plastics are polymers or long chains of atoms bonded to one another. Viewing the atomic structure of plastics is far beyond the scope of this class (If you are interested in such topics, you may want to take AP Chemistry.). • Neon and argon, both gases, are good insulators and are often used in light bulbs. Insulators
- 17. Duration: 60 min DPT Medical Physics Lecture 01 End of Lecture 01 For any kind of queries and questions you are advised to write at [email protected] Or visit my office during consulting hours This lectures can also be downloaded from https://www.slideshare.net/Taimoor_Gondal