Chemistry

How do I learn what chemical element reacts with what other element?
I already know: structure of the atom, aufbau principle, electronegativity, what else do I need?
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You’re already naming the right foundations. To reliably predict what reacts with what, you build a layered mental model. Here’s the complete framework, ordered from most fundamental → most practical.

1️⃣ Atomic structure & quantum rules (the why)

a) Electron configuration (Aufbau + Pauli + Hund)

  • Aufbau → filling order
  • Pauli → max 2 e⁻ per orbital, opposite spin
  • Hund → maximize unpaired electrons

This tells you:

  • Valence electrons
  • Stability (filled vs half-filled shells)
  • Likely oxidation states

Elements react to complete, empty, or stabilize their valence shell.

b) Valence electrons (MOST important early shortcut)

  • Group number ≈ valence electrons (main-group elements)
  • Predicts bonding patterns immediately
Valence e⁻Tendency
1Lose 1 (alkali metals)
2Lose 2
6Gain 2
7Gain 1
8Inert

2️⃣ Electronegativity (WHO pulls electrons)

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Electronegativity answers:

  • Who takes electrons
  • Bond polarity
  • Ionic vs covalent character

Rules of thumb:

  • ΔEN > ~1.7 → mostly ionic
  • Small ΔEN → covalent
  • F, O, N, Cl are aggressive electron pullers

3️⃣ Ionization energy (WHO lets go easily)

  • Low IE → element loses electrons easily
  • High IE → holds electrons tightly

Explains:

  • Why Na reacts violently, Ne doesn’t
  • Why metals oxidize

Trend:

  • ↓ down a group
  • ↑ across a period

4️⃣ Electron affinity (WHO wants electrons)

  • How much energy is released when gaining e⁻
  • High for halogens
  • Complements electronegativity

5️⃣ Orbital overlap & geometry (HOW they bond)

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  • s–s, s–p, p–p overlap quality
  • Hybridization: sp, sp², sp³
  • Determines bond strength & shape

6️⃣ Periodic trends (PATTERN recognition)

You should internalize:

  • Atomic radius
  • Metallic character
  • Reactivity trends

Example:

  • Alkali metals → more reactive down group
  • Halogens → more reactive up group

7️⃣ Oxidation states & redox logic

Every reaction is secretly:

electrons moving

Ask:

  • Who is oxidized (loses e⁻)?
  • Who is reduced (gains e⁻)?

This alone predicts:

  • Metal + non-metal reactions
  • Corrosion
  • Batteries
  • Combustion

8️⃣ Thermodynamics (WILL it happen?)

Even if something can react, ask:

  • ΔG < 0 ? (spontaneous)
  • Enthalpy vs entropy

This explains:

  • Why some reactions need heat
  • Why others explode

9️⃣ Kinetics (HOW FAST?)

  • Activation energy
  • Catalysts
  • Temperature
  • Surface area

Explains:

  • Why diamond doesn’t burn easily
  • Why radicals (•OH) are insane

10️⃣ Special cases you eventually memorize

  • Noble gases (full shells)
  • Transition metals (d-orbitals complicate)
  • Radicals
  • Acids & bases
  • HSAB theory (hard–soft interactions)

🧠 The mental decision tree

When you see two elements:

  1. Valence electrons?
  2. Big electronegativity difference?
  3. Metal vs non-metal?
  4. Who loses e⁻, who gains?
  5. Orbital compatibility?
  6. ΔG negative?
  7. Kinetics reasonable?

If yes to most → reaction likely.

📘 How to actually learn this (practical plan)

Phase 1 (fast intuition)

  • Memorize:
    • Periodic table layout
    • Valence electrons
    • EN trends
  • Practice predicting bonds before checking answers

Phase 2 (deep understanding)

  • MO diagrams
  • Hybridization
  • Redox balancing
  • Thermodynamics basics

Phase 3 (expert intuition)

  • Reaction mechanisms
  • Transition metals
  • Radical chemistry
  • Surface chemistry

One-sentence truth

Chemistry is electrons trying to reach lower energy states — everything else is bookkeeping.

If you want, next I can:

  • Build a step-by-step learning roadmap
  • Give you “reaction prediction drills”
  • Connect this directly to hydroxyl radical chemistry (which you’ve been circling lately)

Just tell me how deep you want to go.