An atom with its first two electron shells completely filled would contain how many electrons?

• A. 12
• B. 18
• C. 8
• D. 10

Answer: (D)

Verified step by step guidance

1. Recall that the first electron shell (the K shell) can hold a maximum of 2 electrons.
2. Recall that the second electron shell (the L shell) can hold a maximum of 8 electrons.
3. Since the problem states that the first two electron shells are completely filled, add the maximum electrons in the first shell and the second shell: \$2 + 8$.
4. Calculate the total number of electrons by summing these values to find the total electrons in the first two shells.
5. Understand that this total represents the number of electrons in an atom with its first two shells completely filled.