Which element has an atom with the electron configuration 2-5, and how many protons does it contain?

• A. 7
• B. 12
• C. 2
• D. 5

Answer: (A)

Verified step by step guidance

1. Understand that the electron configuration 2-5 means the atom has 2 electrons in the first shell and 5 electrons in the second shell.
2. Calculate the total number of electrons by adding the electrons in each shell: \$2 + 5 = 7$ electrons.
3. Recall that in a neutral atom, the number of electrons equals the number of protons, so the atom has 7 protons.
4. Identify the element with 7 protons by referring to the periodic table; the element with atomic number 7 is nitrogen (N).
5. Conclude that the element with electron configuration 2-5 is nitrogen, and it contains 7 protons.