Quantum Mechanical Model of the Atom, Study notes of Chemistry

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Quantum Mechanical Model of the Atom

Updates to Bohr Model:

• Electrons are NOT in circular orbits around nucleus.
• Electrons are in a 3 - D region around the nucleus called atomic orbitals. - The atomic orbital describes the probable location of the electrion Quantum Mechanical Model of the Atom

Where does this model come from? A quick history.

1. Louis de Broglie: Electrons behave with wave and particle properties at the same time.
2. Werner Heisenberg: It is impossible to know both the position and velocity of an electron simultaneously. *Heisenberg's Uncertainty Principle
3. Erwin Shrodinger: Refined the wave-particle theory proposed by de Broglie. Developed an equation that treated an electron like a wave and predicted the probable location of an electron around the nucleus called the *atomic orbital. The quantum mechanical model of the atom treats an electron like a wave.

m⋅ν

h

The quantum mechanical model describes the

probable location of electrons in atoms by describing:

• Principal energy level
• Energy sublevel
• Orbital (in each sublevel)
• Spin

Energy sublevel Principal energy levels are broken down into sublevels.

• Sublevels define the orbital shape (s, p, d, f)

  n= 1 , 1 sublevel (s) n= 2 , 2 sublevels (s, p) n= 3 , 3 sublevels (s, p, d) n= 4 , 4 sublevels (s, p, d, f)

http://edtech 2 .boisestate.edu/lindabennett 1 / 502 /Periodic% 20 Table% 20 e% 20 config/electron% 20 configuration.html Orbitals (in each sublevel) Each sublevel has a different number of orbitals.

• s: 1 orbital
• p: 3 orbitals
• d: 5 orbitals
• f: 7 orbitals

In each principal energy level, there are n 2 orbitals. In each principal energy level, there are a maximum of 2 n 2 electrons. Summary:

Electron Configuration Describes the electron arrangement in atoms. 3 rules for electron configuration at ground state:

1. Aufbau principle : Each electron occupies the lowest energy orbital available.
2. Pauli exclusion principle : A maximum of 2 electrons may occupy a single atomic orbital, but only if they have opposite spins.
3. Hund's rule : a single electron with the same spin must occupy each orbital in a sublevel before they pair up with an electron with an opposite spin.

Next Class: Exceptions to predicted electron configuration. Valence electrons Electron-dot diagrams

HW: Quantum Mechanical Model of the Atom Practice

1. How many electrons are in a hydrogen atom?
2. If the electron of hydrogen is in its ground state, which orbital is it in?
3. How many orbitals are possible at the 3 rd energy level (n= 3 )?
4. Draw the shape of an s and a p orbital.
5. What is the difference between the 2 s and 1 s orbital? How are they similar?
6. How many orbitals are possible at n = 3?
7. How many electrons are possible in n = 3?
8. Write the electron configuration notation for Aluminum.
9. Write the noble gas notation for Aluminum