Template:Keywords: Charge
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Canonical comments on IUPAC definitions in the context of charge
Charge of the proton versus charge per proton
- Proton charge is the elementary charge e [C·x-1], which is charge QelH+ [C] of protons divided by the count NH+ [x] of protons. This distinction is not made sufficiently clear by IUPAC, when defining "-e is the charge of an electron" — it must be corrected to "-e is the charge per electron".
- For comparison, the name "charge density of electrons" is used by IUPAC with symbol ρ [C·m-3]. Dividing ρ by the count concentration of electrons [x·m-3], we obtain the unit [C·x-1] for the electron charge. Therefore, electron charge (or proton charge) is clearly the charge per particle.
Ambiguity of QB
- IUPAC (Cohen 2008 IUPAC Green Book) defines the charge number as
IUPAC: zB = QB·e-1
- Therefore, QB = zB∙e. The subscript in QB indicates per elementary entity B. This is opposite to the subscript in VB as the symbol for the volume of a substance of type B (e.g. VO2 [L]). For consistency with this convention, the symbol QelB or QelX [C] is used for indicating charge of a substance of type B or X, distinguished from particle charge as the quantity of charge per elementary entity X with symbol QUX [C∙x-1]. To avoid too long and multiple subscript levels, QUX is used instead of QUX, and the ‘el’ is dropped from QelUX. The particle charge QUH+ of the proton is defined as elementary charge e. Therefore, the charge number of the proton is zH+ = QUH+/e = 1. In summary:
zB = QUB·e-1
QUB = QelB·NB-1 [C∙x-1]
e ≝ QUH+ = QelH+·NH+-1 [C∙x-1]
Keywords
- » charge QelX
- » charge number zX
- » electrochemical constant f
- » elementary charge e
- » Faraday constant F
- » particle charge QUX
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- Normalization of charge and canonical symbols
Quantity Unit Normalized for quantity Unit Canonical symbol Unit Practical symbol Quantity charge QelX [C] / count NX [x] = QUX [C·x-1] particle charge (IUPAC: QB) charge QelX [C] / amount nX [mol] = QnX [C·mol-1] charge number times Faraday constant charge QelX [C] / volume VX [m3] = QVX [C·m-3] ρel charge density charge QelX [C] / mass mX [kg] = QmX [C·kg-1] specific charge count NX [x] / charge QelX [C] = NeX [x·C-1] amount nX [mol] / charge QelX [C] = neX [mol·C-1] volume VX [m3] / charge QelX [C] = QVX [m3·C-1] ρel-1 mass mX [kg] / charge QelX [C] = MeX [kg·C-1]