III. Modern Atomic Structure

A. Changing Bohr’s Model

  • Schrödinger – Came up with equation that describes the motion of a single electron around a single proton of hydrogen
  • Heisenberg- Says you can’t know where electron is and its is going at the same time (b/c any effort to determine one is going to change it).
  • Heisenberg Uncertainty Principle – can’t actually describe where an electron is in an atom. All you can do is define an area of space around the nucleus where you are most likely to find an electron (Led to orbital theory)
  • Orbital Theory – Electrons are found in orbitals around the nucleus. The orbitals describe regions of space where an electron is most likely to be found at any given moment.
  • s-sublevel – shape of sphere around nucleus. Electron is located somewhere within this space.
  • Quantum Mechanical Model (aka Charge Cloud Model)

B. Describing the Modern Atom

1. Electron Configurations

  • (Each electron has a charge of -1)
  • Each period represents the principle energy level
  • Principle Energy levels are made of Sublevels
  • There are 4 basic sublevel types
  • s-sublevel – can hold up to 2 electrons
  • p-sublevel - can hold up to 6 electrons
  • d-sublevel – can hold up to 10 electrons
  • f-sublevel - can hold up to 14 electrons
  • (# sublevels = principle energy level #)
  • Box Diagrams– show from most general (energy levels) to most specific (orbitals)
  • each sublevel is made of orbitals
  • 1 box=1 orbital
  • Orbital – region of space where you are likely to find 2 electrons, which have opposite spins
  • s-sublevel – 1 orbital (box)
  • p-sublevel - 3 orbital (boxes)
  • d-sublevel – 5 orbitals (boxes)
  • f-sublevel – 7 orbitals (boxes)
  • Spins are represented by arrows (up and down) – up first, followed by down
  • Lewis Dot Structures – 2 dots on each side of letter (maximum amount is 8)
  • Valence electrons – electrons in outermost energy level (most possible is 8 = stable octet)
  • Family 1A 1 valence electron
  • Family 2A - 2 valence electrons
  • Family 3A - 3 valence electrons
  • Family 4A - 4 valence electrons
  • Family 5A- 5 valence electrons
  • Family 6A- 6 valence electrons
  • Family 7A - 7 valence electrons
  • Family 8A – 8 valence electrons
  • Examples –# dots=# of valence electrons
  • Sodium (3s) has 1 valence electron and dot diagram would have a single dot
  • Magnesium (3s2) has 2 valence electrons and has two dots
  • Aluminum has 3 valence electrons has 3 dots
  • Tin (Sn) has 4 valence electrons and 4 dots
  • Nitrogen has 5 valence electrons and 5 dots
  • Oxygen has 6 valence electrons and 6 dots
  • Bromine has 7 valence electrons and 7 dots
  • Argon has 8 valence electrons and 8 dots (stable octet of valence electrons)

2. Quantum Numbers(Electron Zipcode/General Location is space)

  • 4 #’s that recognize a specific electron in orbital notation
  • Principle Energy level/quantum # (n)
  • Range:
  • Ex. 1st principle energy level has a quantum number of 1, 2nd PEL has quantum number of 2, 3, 4, etc.
  • Sublevel (ℓ) – different sublevels are given dif. quantum #’s

ℓ / Sublevel
0 / s
1 / p
2 / d
3 / f
  • Orbital (m ℓ) – which orbital the electron is located in
  • 0 is central orbital
  • Spin (ms) – Box diagram: Up arrow (+ ½), down arrow (- ½)
  • You can name an electron with 4 quantum numbers, and find a specific electron if given the 4 numbers.

3. Atomic Orbitals

a. shapes of orbitals

b. Pauli Exclusion Principle

4. Excited and Ground state

  • Ex. 1s22s233s1 is excited state of Boron b/c skipped over 2p
  • If matches periodic table, it is the ground state
  • If electrons are in a level they are occupied, if they reach maximum amount, then they are full