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The picometre (international spelling as used by the International Bureau of Weights and Measures; SI symbol: pm) or picometer (American spelling) is a unit of length in the International System of Units (SI), equal to 1 × 10 −12 m, or one trillionth ( 1 / 1 000 000 000 000 ) of a metre, which is the SI base unit of length.
The centimetre (SI symbol: cm) is a unit of length in the metric system equal to 10−2 metres ( 1 100 m = 0.01 m). To help compare different orders of magnitude, this section lists lengths between 10 −2 m and 10 −1 m (1 cm and 1 dm). 1 cm – 10 millimetres. 1 cm – 0.39 inches. 1 cm – edge of a square of area 1 cm 2.
Atomic radius. Diagram of a helium atom, showing the electron probability density as shades of gray. The atomic radius of a chemical element is a measure of the size of its atom, usually the mean or typical distance from the center of the nucleus to the outermost isolated electron. Since the boundary is not a well-defined physical entity, there ...
Note: All measurements given are in picometers (pm). For more recent data on covalent radii see Covalent radius.Just as atomic units are given in terms of the atomic mass unit (approximately the proton mass), the physically appropriate unit of length here is the Bohr radius, which is the radius of a hydrogen atom.
Imperial units. 3.937008 × 10 −9 in. Planck units. 6.187 × 1024 lP. The angstrom[1][2][3][4] (/ ˈæŋstrəm /; [3][5][6] ANG-strəm[5]) is a unit of length equal to 10−10 m; that is, one ten- billionth of a metre, a hundred-millionth of a centimetre, [7] 0.1 nanometre, or 100 picometres. The unit is named after the Swedish physicist ...
5.29 × 10−11 m (52.9 pm) The Bohr radius ( ) is a physical constant, approximately equal to the most probable distance between the nucleus and the electron in a hydrogen atom in its ground state. It is named after Niels Bohr, due to its role in the Bohr model of an atom. Its value is 5.291 772 105 44(82) × 10−11 m. [1][2]
Ionic radii are typically given in units of either picometers (pm) or angstroms (Å), with 1 Å = 100 pm. Typical values range from 31 pm (0.3 Å) to over 200 pm (2 Å). The concept can be extended to solvated ions in liquid solutions taking into consideration the solvation shell.
Picotechnology. The term picotechnology is a portmanteau of picometre and technology, intended to parallel the term nanotechnology. It is a hypothetical future level of technological manipulation of matter, on the scale of trillionths of a metre or picoscale (10 −12). This is three orders of magnitude smaller than a nanometre (and thus most ...