An atom of calcium contains 20 protons. How many electrons does it have in its neutral state?

• A. 22
• B. 40
• C. 20
• D. 18

Answer: (C)

Verified step by step guidance

1. Recall that in a neutral atom, the number of electrons equals the number of protons to balance the positive and negative charges.
2. Identify the number of protons in the calcium atom, which is given as 20.
3. Since the atom is neutral, set the number of electrons equal to the number of protons: \(\text{electrons} = 20\).
4. Understand that the mass number (such as 40 or 22) does not affect the number of electrons in a neutral atom; it relates to protons plus neutrons.
5. Conclude that the calcium atom has 20 electrons in its neutral state.