Question

Lithium has 3 protons. how many neutrons are in the isotope lithium -8

Answer 1

It should be 5 neutrons

Answer 2

5 neutrons

Step-by-step explanation:

Both protons and neutrons have a mass of about 1 atomic mass unit (amu). The number in the notation for an isotope is its mass in amu. That means the number is essentially the sum of protons and neutrons in the isotope (electrons don't contribute significantly to the mass).

If lithium has 3 protons, lithium-8 has 8 - 3 = 5 neutrons.