Unit 1: Atoms

The Atomic Theories

  • Heisenburg Uncertainty Principle: it is impossible the exact position and momentum of a single particle.
  • Pioneer of quantum mechanics

Quantum Theory

  • There are 4 sets of number to determine where the electron may be found in an atom
  1. The principle quantum number ‘n’: the energy level of an atom
  2. Secondary Quantum number ‘l’ [0ln-1] is the subdivision of the energy level
  3. Magnetic Quantum number ‘m’ determines orbital type [-lm+l]
  4. Spin Quantum number ‘m’ determines direction of spin [1/2]
  • Note that excited state electrons may move from one energy level to the next level
  • Ground state is when its back to normal

Electron Configuration

  • l letters: s, p, d, f, g, h
  • n values:1 2  3  4 5  6
  • l values:  0 1  2  3 4  5

The Periodic Table

  • Group : up to down, similar properties
  • Period: left to right, metallic to non-metallic
  • Group 1: Alkali            Group 2: Alkaline Earth Metals   Group 17: Halogens   Group 18: Noble Gasses

Trends in Periodic Table

  • Atomic Radius
  1. Decreases from left to right (effective to nuclear charge)  more protons and electrons
  2. Increases from top to bottom (valence electron shielding from the nucleus)
  • Ionization Energy
  1. Is the energy requires to remove an electron from an atom
  2. Increases from left to right 
  3. Decreases from top to bottom because of valence (nuclear shielding)
  • Electron Affinity
  1. The ability for an atom to attract (or take) the electron away from another atom
  2. Increases from left to right
  3. Decreases from top to bottom  because of nuclear shielding.

Chemical Bonding

  • Isoelectronic: same electronic configuration
  • Ionic Bonds
  1.  attraction between negatively charged particle and positive particle USUALLY between a metal and a non-metal
  2. Stable and high melting point
  3. Needs lots of energy to break bond
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  • Covalent Bonds
  1. Sharing of an electron pair (no transfer like in ionic)
  2. Usually between two non-metals
  3. Tend to obtain stable e.c.

Lewis Structures

  • Remember to put formal charge (imaginary )  try to have a formal charge of 0 
  • Formal charge = group number (1-18)  - # of e in lone pairs – ½ (# of e in bond pairs)
  • Truth #1: Elements in the third period and beyond can have more than 8 electrons per shell
  • Boron can have only 6 and still be ok
  • C, N, O, F are goodie-goods. Always follow the rules ...

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