TFNR - Molecules
Molecules (including polyatomic ions) are aggregates of two or more atoms held together by chemical bonds.
They may be formed by atoms of the same kind, or of different chemical elements.
Atoms can be connected by different kind of bonds: covalent bonds, ionic bonds, metal bonds, etc.- and complexes connected by non-covalent interactions, such as hydrogen bonds or ionic bonds, are typically not considered single molecules.
Molecules are the building blocks of compounds, one of the fundamental objects of study of chemistry and molecular physics.
Spatial extension of molecules can span from the very little size of the smaller one, the diatomic hydrogen (with a bond length of 0.74 * 10-10 meters) to the macroscopic sizes of molecules of many inorganic and organic polymers (as proteins and DNA), in the order of around 10-10 to 10-9.
As for atoms, the size and shape of molecules depends on the state and dynamics of the molecule and the state and dynamics of the molecular environment (the compounds of which the molecule take part). Properties of molecules can be intrinsic, mainly due to the interactions with (bonds) and the collective behavior of the atoms (and in turn of the atomic particles, nucleus and electrons) that compose them, and extrinsic, due to the interactions with and the collective behavior or the molecules in the compound.
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