Beryllium has an atomic number of 4. How many neutrons does the isotope beryllium-9have?

Question

(1 point)
4
13
9
5

Answer 1

To determine the number of neutrons in an isotope, you can use the formula:

\[ \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \]

For beryllium-9, the mass number is 9, and the atomic number (which is the number of protons) is 4.

Thus, the calculation is:

\[ \text{Number of neutrons} = 9 - 4 = 5 \]

So, beryllium-9 has 5 neutrons.