Fundamentals
The core facts every aspirant should own — each a titled nugget with a real-world story, the concept in plain words, and a memory trick. Works even when the internet doesn't.
300 fundamentals
“Iron can be Fe²⁺ or Fe³⁺ — which is why blood and rust differ in colour.”
d-block metals show multiple oxidation states and form coloured compounds.
Memory trick: d-electrons → many states, colours.
“Haemoglobin is an iron coordination complex that ferries your oxygen.”
A central metal ion bonded to surrounding ligands that donate electron pairs.
Memory trick: Metal + ligands.
“The fertiliser feeding half the world is made possible by a metal catalyst.”
Catalysts make huge industrial processes economical (iron in the Haber process for ammonia).
Memory trick: Catalysts power industry.
“Too much CO₂ turns Earth's natural blanket into an electric one.”
Gases like CO₂ trap outgoing heat, warming the planet.
Memory trick: CO₂ traps heat.
“The ozone 'sunscreen' high above us blocks rays that would otherwise scorch DNA.”
Stratospheric ozone (O₃) shields life from harmful UV radiation.
Memory trick: Ozone = Earth's UV shield.
“Neon signs glow in set colours because electrons jump fixed rungs.”
Electrons orbit in fixed energy levels; light is emitted or absorbed only in jumps between them.
Memory trick: Energy comes in quantised jumps.
“At the quantum scale, looking closer blurs the picture.”
You cannot know an electron's exact position and momentum simultaneously.
Memory trick: Position and momentum trade off.
“Orbitals are probability clouds, not tracks.”
s orbitals are spherical, p orbitals dumbbell-shaped, d orbitals cloverleaf.
Memory trick: s sphere, p dumbbell.
“Nature bends its own filling rules to reach a more stable arrangement.”
Chromium is 3d⁵ 4s¹ and copper 3d¹⁰ 4s¹ because half- and fully-filled d subshells are extra stable.
Memory trick: Half/fully-filled d = stable.
“The same physics carries your Wi-Fi, warms you as infrared and tans you as UV.”
Light ranges from radio waves to gamma rays; visible light is a thin slice.
Memory trick: Higher frequency = more energy.
“Drop sodium in water and it fizzes, melts and can ignite.”
Group-1 metals are soft, highly reactive and stored under oil.
Memory trick: Reactivity rises down the group.
“Fireworks paint the sky using metal-salt flame colours.”
Alkali and alkaline-earth metals give characteristic flame colours (Na yellow, K lilac, Ca brick-red).
Memory trick: Na = yellow, K = lilac.
“Calcium builds your bones; magnesium sits at the heart of chlorophyll.”
Group-2 metals are harder and less reactive than group-1 and form +2 ions.
Memory trick: Form 2+ ions.
“Lead prefers +2 over +4, which is why lead(IV) is a strong oxidiser.”
Down groups 13–15 the lower oxidation state grows more stable as the s-electrons resist bonding.
Memory trick: Heavier element → lower state favoured.
“78% of every breath is inert nitrogen doing nothing but padding the oxygen.”
N₂ is very unreactive due to a strong triple bond, so it dilutes the air safely.
N≡N
Memory trick: Triple bond → hard to break.
“The same oxide can act as acid or base depending on its partner.”
Non-metal oxides are acidic, metal oxides basic, and some (Al₂O₃, ZnO) are amphoteric.
Memory trick: Metal oxide basic, non-metal acidic.
“Chlorine disinfects your drinking water by its fierce reactivity.”
Group-17 elements are reactive non-metals; reactivity decreases down the group (F > Cl > Br > I).
Memory trick: F is the most reactive.
“Iron rusts red, copper turns green — d-electrons give them their colours.”
d-block metals show variable oxidation states, coloured ions, and catalytic and magnetic behaviour.
Memory trick: d-electrons → colour + catalysis.
“It's why zirconium and hafnium are almost impossible to tell apart.”
A steady size decrease across the lanthanides makes later elements unexpectedly small.
Memory trick: 4f electrons shield poorly.
“Haemoglobin's iron has a coordination number that lets it grab oxygen.”
The number of ligand donor atoms directly bonded to the central metal ion.
Memory trick: Count the metal–ligand bonds.
“Ligands are the metal's chemical 'handshake' partners.”
An ion or molecule that donates an electron pair to a central metal.
Memory trick: Electron-pair donor.
“EDTA's multi-grip makes it a powerful metal remover in medicine and cleaning.”
A ligand that grips a metal at two or more points, forming an extra-stable ring.
Memory trick: Multi-point grip = stable.
“Diamond is crystalline; window glass is a frozen liquid, amorphous.”
Solids are crystalline (ordered) or amorphous (disordered like glass).
Memory trick: Ordered vs disordered.
“A crystal is just one tiny brick copied billions of times.”
The smallest repeating unit that builds a whole crystal lattice.
Memory trick: Repeat unit of a crystal.