They are called symbols.
groups
Usually a single letter code, or a 3 letter code. I've attached a link with both.
The letter (or letters) represents the abbreviation for that element, i.e. it represents the symbol used to represent that element.
I only need to know the one or two letter designation used to represent the name of an element
Chemical symbols represent chemical elements.
They are the symbols for the elements . Often they are some of the letters of the English name.For example, Si means Silicon. Silver cannot be Si as well. Therefore, we use the Latin translation, Argentium, to create Ag.
In science, the letter "j" does not typically represent a specific element or concept. It is simply part of the alphabet used to represent variables, quantities, or labels in equations, formulas, and scientific notation.
A letter used to represent a number is a variable of sometimes a constant.
An elemental symbol, or chemical symbol, represents an element and can be either a single capital letter or a combination of a capital and small letter. For example, the chemical symbol for carbon is "C" and for sodium is "Na".
The letter 'I' is used to represent current. Its SI units are the ampere,(amps),(A).
The letter "I" is typically used to represent electric currents in equations.
A three-letter chemical symbol represents an element in the periodic table. Each element is assigned a unique symbol comprised of one to three letters. These symbols are used in chemical formulas and equations to represent specific elements.