Key idea
Pauli exclusion principle
The Pauli exclusion principle states that no two identical fermions can occupy the same quantum state. In an atom, no two electrons can share all four quantum numbers.
Pauli exclusion principle
The key idea
The Pauli exclusion principle states that no two identical fermions can occupy the same quantum state. In an atom, no two electrons can share all four quantum numbers.
Why it matters
This rule is fundamental to electron-shell structure and therefore to the architecture of the periodic table.
A picture to remember
Key idea
Pauli exclusion principle
+
Guided example
Pauli exclusion principle
The Pauli exclusion principle states that no two identical fermions can occupy the same quantum state. In an atom, no two electrons can share all four quantum numbers.
Put it into practice
Pauli exclusion principle
Choose a concrete case linked to Pauli exclusion principle. Write down the known information, what you are trying to find, and the units. Then state the rule, model or trend you will use. If a calculation is involved, keep the units visible at every line; if it is conceptual, state what changes and what remains fixed.
Check your answer
A strong answer contains four things: the starting situation, the variable that changes, the direction or numerical result, and one check. The check can be a unit, an order of magnitude, a limiting case or a comparison with a familiar example.