protons and electrons grouped together in a random pattern protons and electrons grouped together in an alternating pattern a core of protons and neutrons surrounded by electrons a core of electrons and neutrons surrounded by protons
I gave my students this multiple choice question: Which of the following best describes an atom?

Only one answer is correct among these 4 choices:
- protons and electrons grouped together in a random pattern
- protons and electrons grouped together in an alternating pattern
- a core of protons and neutrons surrounded by electrons
- a core of electrons and neutrons surrounded by protons

Could you tell me which one is correct?

a core of protons and neutrons surrounded by electrons