beryllium has an atomic number of 4. how many neutrons does the isotope beryllium - 9 have? (1 point) 5 9 4 13

Explanation:

Step1: Recall neutron - proton relationship

The mass number of an isotope is the sum of protons and neutrons. For beryllium - 9, the mass number is 9 and the atomic number (number of protons) is 4.

Step2: Calculate number of neutrons

Number of neutrons = Mass number - Atomic number. So, $n=9 - 4$.

Answer:

5