Unit 1 and 2 Notes.docx - UNIT 1 2 NOTES ATOMIC STRUCTURE The History of Atomic Structure Democritus(400 B.C A Greek philosopher the first one to think

Unit 1 and 2 Notes.docx - UNIT 1 2 NOTES ATOMIC STRUCTURE...

This preview shows page 1 - 4 out of 17 pages.

UNIT 1 & 2 NOTES
Image of page 1
ATOMIC STRUCTURE The History of Atomic Structure Democritus (400 B.C.) A Greek philosopher, the first one to think about the existence of atoms. Believed that matter was composed of tiny indivisible particles called atomos (atoms). No experimental evidence. Lavoisier (1743-1794) Worked on combustion reactions and established "Law of Consevation of Mass". First one to realize the importance of combustion supporting gas, oxygen. John Dalton (1766-1844) A meteorologist and teacher. Has supported evidence Dalton's Theory : 1) All elements are composed of extremely small, indivisible particles called atoms . 2) Atoms of the same element have identical shape, size and chemical properties . The atoms of any one element are different from those of another. 3) Atoms of different elements mix or combine in whole number ratios . 4) Chemical reactions occur when atoms seperate, join or rearrange . In a chemical reaction, atoms of 1 element never change into another. J. J. Thomson (1859-1940) - Cathode Ray Tube experiment to discover electrons In the tube was an inert gas, a positive & a negative plates . The gas particles were attacted to the postive plate => The particles must have a negative charge (electrons). "Plum Pudding Model" = atom was a positive sphere with electrons shoved into the sides of it. Ernest Rutherford - Gold Foil Experiment to discover the nucleus Shot high energy beam of positive alpha particles (= 2 protons + 2 neutrons) into gold foil. Expected results: the alpha particles would pass straight through the foil, but: _Most alpha particles went through => the atom was mostly empty space _Few particles were deflected at small angles => the atom contained something small and positive (nucleus) _Very rarely few particles were deflected at large angles => the atom contained a small, very dense and positively charge centre (nucleus). However, he could only account for half the mass of the atom. James Chadwick (1891-1974) - Alpha particles bombardment of the metal beryllium to discover neutrons
Image of page 2
Bohr Model of Atom: Electrons, Flame Tests and AAS _Bohr Model: electrons travel in orbits, or energy levels, around the nucleus. The further the electron is from the nucleus; the more energy it has. _Electromagnetic Spectrum: the classification of electromagnetic waves according to their frequency. _Photons : particles of light energy. Each wavelength of light has photons that have a different amount of energy. The longer the wavelength, the lower the energy of the photons. Why an element’s line spectrum can be used to identify it? When atoms are energized, their ‘excited’ electrons jump to a higher energy level. Because of the instability, the electrons will jump back down to its ground state by releasing the excess energy in the form of light. The wavelengths of the emitted light depend on the difference in energy between the ground state and the excited state. An element has its unique amount of energy in each energy level, so it only emits specific wavelengths and light color.
Image of page 3
Image of page 4

You've reached the end of your free preview.

Want to read all 17 pages?

  • Fall '18
  • maya

What students are saying

  • Left Quote Icon

    As a current student on this bumpy collegiate pathway, I stumbled upon Course Hero, where I can find study resources for nearly all my courses, get online help from tutors 24/7, and even share my old projects, papers, and lecture notes with other students.

    Student Picture

    Kiran Temple University Fox School of Business ‘17, Course Hero Intern

  • Left Quote Icon

    I cannot even describe how much Course Hero helped me this summer. It’s truly become something I can always rely on and help me. In the end, I was not only able to survive summer classes, but I was able to thrive thanks to Course Hero.

    Student Picture

    Dana University of Pennsylvania ‘17, Course Hero Intern

  • Left Quote Icon

    The ability to access any university’s resources through Course Hero proved invaluable in my case. I was behind on Tulane coursework and actually used UCLA’s materials to help me move forward and get everything together on time.

    Student Picture

    Jill Tulane University ‘16, Course Hero Intern

Stuck? We have tutors online 24/7 who can help you get unstuck.
A+ icon
Ask Expert Tutors You can ask You can ask You can ask (will expire )
Answers in as fast as 15 minutes
A+ icon
Ask Expert Tutors