A lithium atom has an atomic number of 3 and a mass number of 7. How many neutrons are in this lithium atom?

• A. 3 neutrons
• B. 10 neutrons
• C. 4 neutrons
• D. 7 neutrons

Answer: (C)

Verified step by step guidance

1. Identify the atomic number of lithium, which is given as 3. The atomic number represents the number of protons in the atom.
2. Identify the mass number of lithium, which is given as 7. The mass number is the sum of protons and neutrons in the atom.
3. To find the number of neutrons, use the formula: \( \text{Number of neutrons} = \text{Mass number} - \text{Atomic number} \).
4. Substitute the known values into the formula: \( \text{Number of neutrons} = 7 - 3 \).
5. Calculate the result to determine the number of neutrons in the lithium atom.