H
Hydrogen
Z = 1
Electrons placed 0 / 1
Score: 0
Level 1 of 14
1s
0
Quantum Rules
Aufbau Principle
Fill lower energy orbitals first: 1s → 2s → 2p → 3s → 3p → 4s → 3d → 4p
Pauli Exclusion
Each orbital holds at most 2 electrons with opposite spins (↑↓)
Hund's Rule
Fill each orbital singly (↑) across a subshell before pairing (↑↓)
How to play
Click a box once for ↑, twice for ↑↓, three times to clear.