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โ† ChemHub

๐Ÿ”ฌ Key Molecules

Eight molecules that shaped chemistry, biology, medicine, and civilisation. Each has a dedicated detail page.

๐Ÿ’ง
Water
Hโ‚‚O  |  18.02 g/mol
"The molecule of life"

The most important molecule on Earth. Its bent shape and polarity give it unique properties: high surface tension, capillary action, excelle...

Bent (104.5ยฐ) Polar inorganic
Full details โ†’
๐ŸŒซ๏ธ
Carbon Dioxide
COโ‚‚  |  44.01 g/mol
"The greenhouse molecule"

Linear and non-polar despite having polar bonds, because the two bond dipoles cancel. Exists as a gas at room temperature. Absorbs infrared ...

Linear (180ยฐ) Non-polar (symmetrical) inorganic
Full details โ†’
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DNA Base Pairs
Cโ‚โ‚€Hโ‚โ‚ƒNโ‚…Oโ‚†P (approx.)
"The molecule of heredity"

Deoxyribonucleic acid encodes all genetic information in living organisms. The double helix is held together by hydrogen bonds between compl...

Double helix Polar (charged backbone) biochemistry
Full details โ†’
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ATP
Cโ‚โ‚€Hโ‚โ‚†Nโ‚…Oโ‚โ‚ƒPโ‚ƒ  |  507.18 g/mol
"The universal energy currency"

Adenosine Triphosphate is the molecule cells use to store and transfer energy. When the terminal phosphate is removed (hydrolysis to ADP), ~...

Complex (adenine + ribose + 3 phosphates) Highly polar biochemistry
Full details โ†’
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Caffeine
Cโ‚ˆHโ‚โ‚€Nโ‚„Oโ‚‚  |  194.19 g/mol
"The world's most used psychoactive drug"

A natural stimulant found in coffee, tea, and cacao. Works by blocking adenosine receptors in the brain. Adenosine normally causes drowsines...

Planar (xanthine ring system) Weakly polar organic
Full details โ†’
๐Ÿ’Š
Aspirin
Cโ‚‰Hโ‚ˆOโ‚„  |  180.16 g/mol
"The most successful drug ever developed"

Acetylsalicylic acid. Works by irreversibly inhibiting COX-1 and COX-2 enzymes, which produce prostaglandins (molecules causing pain, fever,...

Planar benzene ring with acetyl and carboxyl groups Polar organic
Full details โ†’
๐Ÿท
Ethanol
Cโ‚‚Hโ‚…OH  |  46.07 g/mol
"The oldest human chemical"

The alcohol in alcoholic drinks. Acts on GABA receptors (inhibitory) and NMDA receptors (excitatory) in the brain, producing sedation. Produ...

Tetrahedral at C atoms; bent O-H Polar (hydroxyl group) organic
Full details โ†’
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Sodium Chloride
NaCl  |  58.44 g/mol
"The mineral of civilisation"

Table salt. An ionic compound forming a 3D crystal lattice where each Naโบ is surrounded by 6 Clโป and vice versa. High melting point (801ยฐC) ...

Face-centred cubic crystal lattice Ionic (not molecular) inorganic
Full details โ†’

๐Ÿ”— Bond Types

Every type of chemical bond, from ionic to Van der Waals - what holds molecules together and why it matters.

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Ionic
Strong (in solid)
NaCl, MgO, CaCOโ‚ƒ

Complete transfer of electrons. Forms between metals and non-metals. High melting point. Conducts when dissolved/molten.

๐Ÿ”—
Covalent (single)
Moderate
Hโ‚‚, Hโ‚‚O, CHโ‚„

Sharing of 2 electrons (1 pair). C-H bonds in all organic molecules. Can be polar or non-polar.

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Covalent (double)
Stronger than single
Oโ‚‚, COโ‚‚, Cโ‚‚Hโ‚„

Sharing of 4 electrons (2 pairs). Shorter and stronger than single bonds. Alkenes contain C=C.

๐Ÿ’ช
Covalent (triple)
Strongest covalent
Nโ‚‚, Cโ‚‚Hโ‚‚

Sharing of 6 electrons (3 pairs). Nโ‚‚ triple bond is the strongest diatomic bond (945 kJ/mol). Very unreactive.

๐Ÿค
Hydrogen bond
Weak (10-40 kJ/mol)
Hโ‚‚O, DNA, proteins

Attraction between ฮด+ H and lone pair on O, N, or F. Individually weak but collectively crucial for DNA, water, and protein structure.

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Metallic
Variable
Fe, Cu, Al, Na

Sea of delocalised electrons. Explains conductivity, malleability, ductility, and metallic lustre. Stronger in metals with more delocalised electrons.

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Van der Waals
Very weak
Noble gases, Iโ‚‚, CHโ‚„

Temporary dipoles from electron movement. Only force between non-polar molecules. Explains why noble gases can be liquefied at low temperatures.