How many neutrons are present in an atom of hydrogen-3 (tritium)?

• A. 3
• B. 1
• C. 2
• D. 0

Answer: (C)

Verified step by step guidance

1. Step 1: Understand the structure of an atom. An atom consists of protons, neutrons, and electrons. The number of protons determines the atomic number, while the sum of protons and neutrons gives the mass number.
2. Step 2: Identify the given isotope. Hydrogen-3 (tritium) is an isotope of hydrogen with a mass number of 3. The mass number is the total number of protons and neutrons in the nucleus.
3. Step 3: Determine the number of protons. Hydrogen always has 1 proton, as its atomic number is 1. This is consistent across all isotopes of hydrogen.
4. Step 4: Calculate the number of neutrons. Use the formula: $\mathrm{Number} \mathrm{of} \mathrm{neutrons}=\mathrm{Mass} \mathrm{number} - \mathrm{Number} \mathrm{of} \mathrm{protons}$. For hydrogen-3, the mass number is 3 and the number of protons is 1.
5. Step 5: Subtract the number of protons from the mass number. This gives the number of neutrons: $3-1$. The result is the number of neutrons in hydrogen-3.