Identify element by atomic structure in diagram

Steps:

• Examine the atomic model to count protons in the nucleus.
• Confirm atomic number matches the proton count.
• Compare to periodic table elements with that atomic number.
• Select the matching element from choices.

Why A is correct:

• Beryllium has atomic number 4, matching a nucleus with 4 protons as per atomic theory.

Why the others are wrong:

• B: Boron has 5 protons, not matching the diagram.
• C: Carbon has 6 protons, not matching the diagram.
• D: Magnesium has 12 protons, not matching the diagram.

Final answer: A