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Section 5.3

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Section 5.3

Electron Configurations

- Atom is in the ground state
- 3 rules or laws
- Aufbau principle
- Pauli Exclusion principle
- Hund’s Law

- Electrons occupy lowest energy orbital available
- All orbitals of a sublevel are equal energy
- Sublevels have different energies
- s < p < d <f

- Orbitals within one principal energy level can overlap orbitals of another

Which orbital will fill first, 4s or 3d?

- Maximum of 2 electrons in an orbital, but only if they have opposite spin.

- Electrons with same spin must occupy each equal energy orbital before additional electrons with opposite spins can occupy the same orbital.

1s 2s 2p 3s 3p 4s

3d 4p 5s 4d 5p 6s

4f 5d 6p 7s 5f 6d 7p

- Three methods
1. Electron Configuration Notation

2. Noble Gas Notation

3. Orbital Diagrams

- Ex: N
- # of electrons?

- Start with the lowest energy, fill to capacity, go to next lowest energy, etc. Stop when you run out of electrons.
- Superscripts = total electrons

- You try … Zinc

1s2 2s22p6 3s23p6 4s23d10

- Write the electron configuration notation for the following elements:
- Boron (B), Neon (Ne), Sulfur (S), Magnesium (Mg), Vanadium (V), Silver (Ag)

- Shorthand
- Find the noble gas closest to the element (without going over).
- Ex: For Gold (79): Xenon (54)
- We write [Xe] and start counting from there
- The first orbital after xenon is 6s

- [Xe]6s2 4f14 5d9
- Check: (Xe’s atomic number) 54 + 2 + 14 + 9 = 79 (gold’s Atomic number)!

- Silver

- P.147 #79

- Draw a line for each orbital
- Designate each electron with an arrow
- = orbital with 1 electron
- = orbital with 2 electrons

- Nitrogen: 1s22s22p3
- Write notation of N
- Then we fill them with electrons using the Aufbau principle, Pauli exclusion principle, and Hund’s law

- You try another example: Cu

- Answer

- Draw orbital diagrams for beryllium, aluminum, nitrogen, and sodium, manganese, germanium, and europium.

- Valence electrons
- Electrons in outermost energy level.
- Responsible for chemical properties

- Valence electrons only
- Place ‘dots’ around element symbol
- 4 sides of element = orbitals
- Fill these orbitals one at a time (Hund’s)

- P.141 #23(yellow box), 26, 28
- P.147 #81