Chemistery

Both hold molecules together from the outside, both are far weaker than a real bond — so why does one get a special name? Hydrogen bonds and van der Waals forces sit in the same family, but the gap in strength between them explains some of chemistry's biggest surprises, like why water boils at 100 °C when it "should" boil far colder. The short answer: van der Waals forces are the weak, general attractions between molecules — mainly London dispersion forces and dipole–dipole forces . A hydrogen bond is a much stronger, special attraction that forms only when hydrogen is bonded to nitrogen, oxygen, or fluorine and is drawn to a lone pair on an N, O, or F in another molecule. Both are intermolecular forces; the hydrogen bond is just the strongest of the group. Quick comparison at a glance Feature Van der Waals forces Hydrogen bonds What they include London dispersion + dipole–dipole A special, strong dipole–dipole case Where they occur Between all mo...

You've met ionic bonds (electrons transferred) and covalent bonds (electrons shared). But what holds a lump of pure copper or iron together, when there's only one kind of atom and nobody to trade with? That's the job of the third great bond type: metallic bonding . The short answer: metallic bonding is the attraction between positively charged metal ions and a " sea " of shared, freely moving electrons. Metal atoms give up their outer (valence) electrons into a common pool that flows through the whole structure, and the electrostatic pull between the fixed positive ions and this mobile electron sea holds the metal together. What metallic bonding actually is Picture a metal as a neat 3D lattice of positive ions (metal atoms that have released their valence electrons) sitting in a shared pool of those delocalised electrons . "Delocalised" means the electrons don't belong to any single atom — they roam freely across the entire piece of metal. The...

You've drawn double bonds as two lines and triple bonds as three — but are those lines all the same? They're not. A double bond is really two different kinds of bond stacked together, and knowing the difference explains everything from bond strength to why some molecules can't twist. The short answer: a sigma (σ) bond forms when two orbitals overlap end-to-end , concentrating the shared electrons directly along the line between the two nuclei. A pi (π) bond forms when two p orbitals overlap side-by-side , placing electron density above and below that line. Every single bond is one sigma bond; double and triple bonds add pi bonds on top. Quick comparison at a glance Feature Sigma (σ) bond Pi (π) bond Orbital overlap End-to-end (head-on) Side-by-side (parallel p orbitals) Where the electrons sit Directly between the nuclei Above and below the bond axis Relative strength Stronger (more overlap) Weaker (less overlap) Rotation around the bond Fr...

Here's a puzzle that catches almost everyone: water (H₂O) is polar, but carbon dioxide (CO₂) is not — even though both are built from polar bonds. The answer isn't in the bonds at all. It's in the shape. The short answer: a polar molecule is one with an overall (net) separation of charge — a slightly positive end and a slightly negative end. That happens when a molecule has polar bonds and a shape lopsided enough that those bond dipoles don't cancel out. If the shape is symmetric and the pulls cancel, the molecule is nonpolar even with polar bonds. What "polar molecule" actually means Every polar bond has a little arrow of charge called a dipole , pointing from the δ+ atom toward the δ− atom. A molecule can have several of these arrows at once. To find the molecule's overall polarity, you add the arrows up like tug-of-war teams pulling in different directions: If the arrows cancel (equal and opposite), there's no net pull → nonpolar molecu...

The names look almost identical, and that one syllable — intra vs inter — trips up thousands of students every exam season. Get it straight once and a whole chunk of chemistry (boiling points, states of matter, why ice floats) clicks into place. The short answer: intramolecular forces are the bonds inside a molecule that hold its atoms together (ionic, covalent, metallic) — they're strong. Intermolecular forces are the weaker attractions between separate molecules. The prefixes are the whole trick: intra means "within," inter means "between." Quick comparison at a glance Feature Intramolecular forces Intermolecular forces Where they act Within one molecule (atom to atom) Between separate molecules What they are Ionic, covalent, metallic bonds Dispersion, dipole–dipole, hydrogen bonds Relative strength Strong (~100–1000 kJ/mol) Weak (~1–40 kJ/mol) What breaking them means A chemical reaction A change of state (melt/boil) ...

Chemistry throws molecular formulas at you like H₂O and CO₂, but a formula doesn't show how the atoms actually connect. A Lewis structure is the little dot-and-line drawing that fills in that gap — and once you can draw one, molecules stop being mysterious. The short answer: a Lewis structure (or electron-dot structure) is a diagram that shows how the valence electrons of atoms are arranged in a molecule. Shared pairs (the bonds) are drawn as lines, and unshared pairs (lone pairs) are drawn as dots, so you can see at a glance which atoms are bonded and where the leftover electrons sit. What a Lewis structure actually shows A Lewis structure tracks only the valence electrons — the outer-shell electrons that do the bonding. It uses two symbols: A line = a bonding pair (two shared electrons). A double line is two shared pairs; a triple line is three. A pair of dots = a lone pair (two electrons that belong to one atom and aren't shared). The goal is usually to give e...