Metals, non-metals, metalloids — properties
The one root cause
WHY does "electron behaviour" decide everything? Because all bulk properties come from how electrons move:
- If electrons are loosely held and free to roam → a "sea of electrons" → conducts electricity/heat, is shiny, bendable → metal.
- If electrons are locked into fixed bonds → no free carriers → insulator, brittle, dull → non-metal.
- If electrons are half-free → conducts a little, more when heated → metalloid (semiconductor).
Deriving the property list (don't memorise — reason!)
| Observation | WHY (from the model) |
|---|---|
| Conducts electricity | Free electrons drift when a voltage is applied. |
| Conducts heat | Free electrons carry kinetic energy quickly across the solid. |
| Malleable & ductile | Layers of ions slide past each other; the electron sea just re-flows, no bonds snap. |
| Shiny (lustrous) | Free electrons absorb & re-emit light. |
| Forms + ions / basic oxides | Loses electrons → cations; oxide + water → base. |
| Observation | WHY |
|---|---|
| Insulator | No free carriers. |
| Brittle | Push a layer and like-charges/bonds clash → shatters instead of sliding. |
| Dull | No electron sea to reflect light. |
| Forms − ions / acidic oxides | Gains electrons → anions; oxide + water → acid. |
The metalloid staircase
WHY semiconductors? Their electrons are almost free but need a small energy nudge (heat/light/doping) to conduct. That controllable "in-between" conduction is exactly why Si and Ge run every computer chip — the 80/20 fact worth remembering.
Worked examples
Common mistakes (Steel-man them!)
Active recall
What single atomic tendency defines a metal?
Metallic character is inversely proportional to which quantity?
Across a period, metallic character does what and why?
Down a group, metallic character does what and why?
Where on the table is the most metallic element (excluding noble gases)?
Name the metalloids.
Why do metals conduct electricity?
Why are non-metals brittle?
Metal oxide + water gives a ___ ; non-metal oxide + water gives a ___.
How does a semiconductor's conductivity change with temperature vs a metal's?
Why is graphite a conducting non-metal?
Recall Feynman: explain to a 12-year-old
Imagine every atom is a kid holding balloons (electrons). Metal kids hold their balloons loosely — bump them and the balloons float around freely, so "messages" (electricity) zip through the crowd, and the kids can shuffle without dropping anyone (bendable). Non-metal kids grip their balloons tight, even snatch extras — nothing floats free, so no messages pass (insulator), and if you shove them they trip and scatter (brittle). Metalloid kids hold their balloons sort of loosely — they'll let a few go only if you warm them up (semiconductors — the stuff computer chips are made of). One rule — how tightly you hold your balloon — explains everything.
Connections
- Ionisation Energy — the root cause of metallic character.
- Electronegativity — the mirror concept for non-metals.
- Periodic Trends — Atomic Radius — explains why IE changes.
- Acidic and Basic Oxides — chemical consequence of the metal/non-metal split.
- Electronic Configuration — decides how many electrons are lost/gained.
- Semiconductors and Doping — the technology born from metalloids.
Concept Map
Hinglish (regional understanding)
Intuition Hinglish mein samjho
Dekho, poori cheez ek hi baat pe tiki hai: element apne bahar wale electrons ko kitni asaani se chhodta ya pakadta hai. Agar element electron aaram se de deta hai (matlab kam ionisation energy), toh wo metal hai — shiny, bijli-heat conduct karega, hammer se pital jaisa faila sakte ho (malleable). Agar element electron ko zor se pakadta hai ya cheen leta hai (high electronegativity), toh wo non-metal hai — dull, brittle, current nahi le jaata.
Ab yaad rakhne ka smart tareeka: alag-alag properties ratne ki zaroorat nahi. Metals mein ek "sea of electrons" hota hai — free electrons taerte rehte hain, isliye current chalti hai, heat travel karti hai, aur atoms slide kar jaate hain isliye bend hota hai. Non-metals mein electrons fixed bonds mein locked hote hain, isliye insulator aur brittle. Bas electron free hai ya nahi — yahi soch ke har property nikaal lo.
Metalloids (B, Si, Ge, As, Sb, Te) staircase ke border pe baithe hain — beech waale. Ye semiconductor hote hain: thodi si heat ya doping se conduct karne lagte hain. Isiliye computer chips Silicon ke bante hain — yeh 80/20 wali sabse zaroori baat hai.
Trend ka rule simple hai: metallic character = 1/ionisation energy. Period mein left se right jao toh nuclear charge badhta hai, radius chhota hota hai, electron zyada tight, IE badhti hai — toh metallic character kam. Group mein neeche jao toh radius bada, shielding zyada, electron loose, IE kam — toh metallic character zyada. Isliye sabse zyada metal bottom-left (Cs, Fr) aur sabse zyada non-metal top-right (F, O, Cl). Bas yahi core hai, exam mein kahin bhi laga do.