Template:Keywords: Charge

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 Q_elH⁺ [C] of protons divided by the count N_H⁺ [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 Q_B

IUPAC (Cohen 2008 IUPAC Green Book) defines the charge number as

IUPAC:  zB = QB·e-1

Therefore, Q_B = z_B∙e. The subscript in Q_B indicates per elementary entity B. This is opposite to the subscript in V_B as the symbol for the volume of a substance of type B (e.g. V_O2 [L]). For consistency with this convention, the symbol Q_elB or Q_elX [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 Q_UX [C∙x^-1]. To avoid too long and multiple subscript levels, Q_UX is used instead of Q_UX, and the ‘el’ is dropped from Q_elUX. The particle charge Q_UH⁺ of the proton is defined as elementary charge e. Therefore, the charge number of the proton is z_H⁺ = Q_UH⁺/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 Q_elX

» charge number z_X

» electrochemical constant f

» elementary charge e

» Faraday constant F

» iconic symbols

» particle charge Q_UX

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Normalization of charge and iconic symbols

Iconic symbols show the quantity, the format of the normalization in the subscript (U, n, e), and the entity specified in the subscript (X). The normalized quantities are per X. In the quantities Q_elX, N_X, n_X, V_X, m_X, the subscript X without attachment to a format indicates the quantity of X.

Quantity	Unit	Normalized for quantity	Unit	Iconic 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]	= VeX	[m3·C-1]	ρel-1
mass mX	[kg]	/ charge QelX	[C]	= meX	[kg·C-1]