Chem 17 Reviewer (1st Exam)

1512 Words Dec 29th, 2011 7 Pages
CHEMISTRY 17 1ST LONG EXAM REVIEWER I. ELECTRONIC STRUCTURE OF ATOMS

-arrangement of atoms’ electrons
-the number of electrons in an atom
-distribution of electrons around the nucleus and their energies

• ATOMS *Billiard Ball Model (JOHN DALTON) *Plum Pudding Model (JOSEPH J. THOMPSON)
*RUTHERFORD’s Model of Atom
-atoms are tiny, hard, indivisible spheres
-electrons (negative charge) occupy the atom

- Atom is mostly empty space with a dense nucleus
• PROBLEMS with Rutherford’s Model *According to laws of physics, Rutherford’s atom should collapse
*The model CANNOT explain differences in properties of elements
*The model CANNOT explain the colors emitted by elements when heated A. THE QUANTUM MODELS (WAVE)
-formed
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 An electron in a permitted orbit has a specific energy and is in an allowed energy state. An electron in an allowed energy state will not spiral into the nucleus.
 Energy is transmitted or absorbed by the electron only as the electron changes from one allowed energy state to another. This energy is emitted or absorbed as a photon, E= hѵ.
• For electron to move farther from the nucleus, it needs more potential energy. o Distance from the nucleus of an allowed orbit, n. o Energy of the electron in the allowed orbit, n. ↔

o Applications
 Fireworks
 Use of emission spectroscopy to analyse for the presence of elements.
• Success of Bohr Model o It successfully predicted the frequencies of the lines in the hydrogen spectrum o It introduced the concept of discrete energy levels of electron in atoms and the first quantum number, n. o The model failed to predict energy levels for atoms with more than 1 electron. (if 2/more electrons are present, the electrons repel)

D. THE WAVE BEHAVIOR OF MATTER
• Louis de Broglie (1892-1987) o “Depending on the experimental circumstances, radiation appears to have either a wavelike or a particle-like (photon) character.” o **As the electron moves

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