Question

describing isotopes what is the mass number of the isotope lithium - 7? lithium has 3 protons. how many neutrons are in the isotope lithium - 8?

Explanation:

Step1: Identify mass number notation

For isotope lithium-7, the suffix after the element name is the mass number.
Mass number of lithium-7 = $7$

Step2: Calculate neutrons for lithium-8

Use formula: $\text{Neutrons} = \text{Mass number} - \text{Protons}$
Substitute values: $\text{Neutrons} = 8 - 3 = 5$

Answer:

Mass number of lithium-7: $7$
Number of neutrons in lithium-8: $5$