| FISSION | A splitting, as of atoms |
| CLEAVER | Chops primarily one's splitting, as tool (7) |
| ISOTONE | One of a group of atoms having the same number of neutrons but a different number of protons |
| CRYSTAL | From the Greek for "ice, frost", an array of atoms forming a polyhedral solid, such as a diamond, moonstone, piece of rock salt or a snowflake (7) |
| CHAIN | Bonded sequence of atoms forming a molecule; or, a series of connected events, house purchases, daisies, mountains or metal links (5) |
| RING | Closed chain of atoms; or, any one of the discs consisting of millions of moonlets orbiting Saturn (4) |
| METAMER | Compound that contains the same number and type of atoms as other compounds but with a different distribution of radicals |
| TAUTOMER | Either of two or more isomers of a chemical compound existing together in equilibrium and interconvertible by migration of atoms and bonds (8) |
| FREERADICAL | An atom or group of atoms containing at least one unpaired electron and existing for a brief period of time before reacting to produce a stable molecule |
| NUCLEARPHYSICS | A branch of science studying the structure of the central core of atoms (7,7) |
| STERIC | Of the spatial relationship of atoms in a molecule |
| LATTICE | A regular periodic arrangement of atoms, ions, or molecules in a crystalline solid |
| ISOMERISM | Property of having the same formula but a different arrangement of atoms |
| VORTEX | A whirl of atoms, fluid or vapour forming a cavity in the centre (6) |
| COMPOUND | Any substance made up of identical molecules consisting of atoms of two or more chemical elements. |
| TRICYCLIC | Of a chemical compound, having three interconnected rings of atoms in its molecular structure (9) |
| STOMA | It's like a mouth made of atoms (5) |
| CRYSTALLATTICE | Three-dimensional arrangement of atoms inside a diamond, say |
| ISOMER | Same compound with a different arrangement of atoms |
| MOLECULE | What is a group of atoms bonded together? (8) |
