How many protons (p) and neutrons (n) are present in an atom of calcium-46?

• A. 26 protons and 20 neutrons
• B. 20 protons and 26 neutrons
• C. 46 protons and 20 neutrons
• D. 20 protons and 46 neutrons

Answer: (B)

Verified step by step guidance

1. Identify the atomic number of calcium, which is the number of protons in the atom. Calcium has an atomic number of 20, so it has 20 protons.
2. Understand that the number after the element name (46 in calcium-46) is the mass number, which is the total number of protons and neutrons in the nucleus.
3. Use the formula for the number of neutrons: \(\text{Number of neutrons} = \text{Mass number} - \text{Number of protons}\).
4. Substitute the known values: \(\text{Number of neutrons} = 46 - 20\).
5. Calculate the number of neutrons to find how many neutrons are present in calcium-46.