Hey there!
In hyphenated notation, we have the name of the element, a hyphen, then a number that is the sum of protons and neutrons.
The first isotope has 3 protons and 3 neutrons, so the sum is 6. Its name is lithium-6.
The second isotope has 3 protons and 4 neutrons, so the sum is 7. Its name is lithium-7.
Hope this helps!
