Question

1. how many protons, neutrons, and electrons are in a neutral isotope of beryllium with a mass number of 9 and an atomic number of 4?

4 protons, 4 electrons, 4 neutrons
4 protons, 4 electrons, 5 neutrons
4 protons, 4 electrons, 9 neutrons
5 protons, 5 electrons, 4 neutrons

Explanation:

Step1: Determine the number of protons

The atomic number \(Z\) of an element is equal to the number of protons. Given that the atomic number of beryllium is \(4\), so the number of protons \(p = 4\).

Step2: Determine the number of electrons

For a neutral atom, the number of electrons \(e\) is equal to the number of protons. Since \(p = 4\), then \(e=4\).

Step3: Determine the number of neutrons

The mass number \(A\) is given by the formula \(A=p + n\), where \(n\) is the number of neutrons. Rearranging the formula gives \(n=A - p\). Given \(A = 9\) and \(p = 4\), then \(n=9 - 4=5\).

Answer:

4 protons, 4 electrons, 5 neutrons