You think probable to atomic number.
It is the state of ionisation.
the number above the symbol is the atomic....... of that element.
There is no symbol above the number 0 on my phone keyboards. So clearly, it is not a standard.
The atomic number.
A power or exponent.
It is the power, index or exponent.
A number with a line above it - 4
@ It is the symbol above the number 2 on the QWERTY keyboard.
Mass number
The Atomic Number and thus the number of protons
ampersand
atomic number