Q
QuestionChemistry

How many protons, neutrons, and electrons are present in an atom of argon (Ar) with a mass number of 40? A. 18 protons, 22 neutrons, 18 electrons B. 18 protons, 40 neutrons, 22 electrons C. 22 protons, 18 neutrons, 22 electrons D. 40 protons, 58 neutrons, 18 electrons
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Answer

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Step 1
: Identify the number of protons, which is equal to the atomic number of argon.

\text{Number of protons} = 18
The atomic number of argon is 18. Therefore, there are 18 protons in an argon atom.

Step 2
: Determine the number of electrons based on the number of protons (since argon is a neutral atom).

\text{Number of electrons} = 18
In a neutral atom, the number of electrons is equal to the number of protons. So,

Final Answer

The correct answer is A. 18 protons, 22 neutrons, 18 electrons.