Is there a canonical variable for period and group?

Question

For example, "Z" is the standard symbol for atomic number. I'm writing a manuscript that uses the group and period of elements within some equations, and so far I'm just denoting them as $G_{table}$ and $P_{table}$, defining them in the paragraph before the equation is presented. But there are a couple of concerns with that, namely:

1. If there is a canonical symbol that I forgot after undergrad, I'll look rather silly to a reviewer
2. A reader skimming the paper might confuse those symbols for Gibbs free energy or pressure

Is there a standard variable that's commonly used to denote the group or period of an element within an equation?

Answer 1

There isn't a standard symbol. However, if you choose these current symbols, please note that "table" should be placed in upright font, not italics:

• correct: G_{\text{table}} $G_{\text{table}}$
• wrong: G_{table} $G_{table}$

The reason is because "table" is a plain old English word. You can see Which symbols are written in roman (upright) font and which are italicized? for more information; even though that post was written mainly for Chem.SE, the information there is applicable to all of chemistry. The IUPAC Green Book writes (Section 1.3.1)

Subscripts and superscripts that are themselves symbols for physical quantities or for numbers should be printed in italic type; other subscripts and superscripts should be printed in Roman (upright) type.

and other sources such as the ACS Style Guide have similar recommendations.

Personally, if I were you I'd just cut the subscript altogether, unless it's likely to lead to confusion. No need for clunky symbols. For example, Euler's polyhedron formula usually just reads

$$V - E + F = 2$$

instead of something like

$$n_\text{vertex} - n_\text{edge} + n_\text{face} = 2.$$