Let’s go step by step to understand what this diagram is showing and how to use it.
This chart shows the electron configuration for elements from Hydrogen (H) to Calcium (Ca), using boxes and arrows. Each box represents an orbital, and each arrow represents an electron. The direction of the arrow (up or down) shows the electron’s spin.
The labels like “1s”, “2s”, “2p”, etc., tell us which energy level and sublevel we’re looking at:
- The number (1, 2, 3...) is the principal energy level.
- The letter (s, p, d, f) tells us the shape of the orbital.
- s holds up to 2 electrons → 1 box
- p holds up to 6 electrons → 3 boxes
- d holds up to 10 → 5 boxes (not shown here yet)
- f holds up to 14 → 7 boxes (not shown here)
Electrons fill orbitals in order: 1s → 2s → 2p → 3s → 3p → 4s → 3d...
Also, remember Hund’s Rule: when filling orbitals of equal energy (like the three 2p boxes), you put one electron in each box first (all with same spin — usually up), then pair them up.
Now, let’s look at a few examples to make sure we get it:
→ Hydrogen (H): atomic number = 1 → 1 electron → goes in 1s ↑
→ Helium (He): atomic number = 2 → 2 electrons → 1s ↑↓
→ Lithium (Li): atomic number = 3 → 1s² 2s¹ → so 1s has two arrows (↑↓), 2s has one (↑)
→ Beryllium (Be): 4 electrons → 1s² 2s² → both 1s and 2s are full (↑↓ each)
→ Boron (B): 5 electrons → 1s² 2s² 2p¹ → now we start filling 2p. First electron goes in first 2p box ↑
→ Carbon (C): 6 electrons → 1s² 2s² 2p² → second electron in 2p goes in next box ↑ (same spin, per Hund’s rule)
→ Nitrogen (N): 7 electrons → 1s² 2s² 2p³ → all three 2p boxes have one ↑ electron
→ Oxygen (O): 8 electrons → 1s² 2s² 2p⁴ → now we start pairing: first 2p box gets ↓, others still ↑
And so on...
Looking at Sodium (Na): atomic number 11 → after Neon (10 electrons: 1s² 2s² 2p⁶), the 11th electron goes into 3s → so 3s has ↑
Magnesium (Mg): 12 electrons → 3s² → 3s has ↑↓
Aluminum (Al): 13 electrons → 3p¹ → first 3p box gets ↑
Silicon (Si): 14 electrons → 3p² → second 3p box gets ↑ (same spin)
Phosphorus (P): 15 electrons → 3p³ → all three 3p boxes have ↑
Sulfur (S): 16 electrons → 3p⁴ → first 3p box gets ↓
Chlorine (Cl): 17 electrons → 3p⁵ → second 3p box gets ↓
Argon (Ar): 18 electrons → 3p⁶ → all 3p boxes full (↑↓ each)
Potassium (K): 19 electrons → after Argon, next is 4s → 4s¹ → ↑
Calcium (Ca): 20 electrons → 4s² → ↑↓
Everything matches the rules!
So if someone asks you to write the electron configuration for any element up to Ca, you can count the total electrons (same as atomic number), and fill the boxes in order: 1s, 2s, 2p, 3s, 3p, 4s — following Pauli Exclusion (max 2 per box, opposite spins) and Hund’s Rule (fill singly before pairing).
You don’t need to memorize every single one — just know the order and the rules, and you can build it yourself.
Final Answer: This chart correctly shows the electron configurations for elements H through Ca using orbital diagrams, following the Aufbau principle, Pauli exclusion principle, and Hund’s rule.
Parent Tip: Review the logic above to help your child master the concept of atomic orbitals worksheet.
