# Chapter 5 Section 5.2

```Do Now:
Complete
Protons, Neutrons, and Electrons
Practice Worksheet
YWBAT
• List the three rules for writing the electron
configuration of elements
Electron Configuration
• Describes arrangement of electrons in an
atom
• Three rules
1. Aufbau Principle
2. Pauli Exclusion Principle
3. Hund’s rule
Electron Configuration
1. Aufbau Principle
a) An electron occupies the lowest energy orbital
b) Fill electrons lowest to highest energy
2. Hund’s Rule
- Orbitals of the same energy must be occupied by 1
electron before it can be occupied by two electrons
3. Pauli-Exclusion Principle
- Each orbital can only hold 2 electrons with opposite
spins
The aufbau diagram shows the
relative energy levels of the various
atomic orbitals. Orbitals of greater
energy are higher on the diagram.
Practice
Phosphorus has 15 electrons. Write the
electron configuration for Phosphorus.
Practice
Phosphorus has 15 electrons. Write the
electron configuration for Phosphorus.
1s22s22p63s23p3
Noble Gas Configuration
1. Find the element on the periodic table.
2. Go back to the last noble gas that was
passed.
3. Write the symbol of the noble gas in brackets
4. Continue your electron configuration using
the row after the noble gas.
Noble Gas Configuration
Write the noble gas configuration for Osmium.
- Osmium is element 76.
- The last noble gas was Xenon.
- Os: [Xe] 6s2 4f14 5d6
Quantum Number Review
• Principle Quantum Number (n)
– Energy level
– Row on periodic table
• Angular Quantum Number (l)
– Sublevels (s,p,d,f)
– # sublevels = principle quantum number
• # of orbitals = n2
• Maximum number of electrons that can
occupy an energy level is 2n2
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