Question

most neutral atoms of argon have an atomic mass of 40 amu and an atomic number of 18. what are these atoms composed of? a. 18 protons, 22 neutrons, and 18 electrons b. 18 protons, 22 neutrons, and 22 electrons c. 18 protons, 18 neutrons, and 18 electrons d. 18 protons, 40 neutrons, and 18 electrons

Explanation:

Step1: Determine the number of protons

The atomic number of an element is equal to the number of protons in its atom. Given that the atomic number of argon is 18, so the number of protons \(p = 18\).

Step2: Determine the number of electrons

For a neutral atom, the number of electrons \(e\) is equal to the number of protons. Since \(p=18\), then \(e = 18\).

Step3: Determine the number of neutrons

The atomic mass \(A\) is the sum of the number of protons \(p\) and neutrons \(n\). We know that \(A = 40\) and \(p=18\). Using the formula \(A=p + n\), we can solve for \(n\):

$$n=A - p$$

$$n=40-18$$

$$n = 22$$

Answer:

A. 18 protons, 22 neutrons, and 18 electrons