What is the isotope notation for lithium?

It depends on the specific isotope of lithium that you're talking about. Lithium has five , and each will have different notation.

For example, the for lithium-7 is: ##._3^(7)Li##

Lithium-7 is commonly used in salt and nuclear reactors.

##._(A)^ZX##, where X is the atomic symbol for the element, here Li for lithium, Z is the , or the total number of protons and neutrons, and A is the , or the number of protons.