Which of the following is a part of an atom? a. proton
b. neutron
c. electron
d. all of the above

except for hydrogen (a proton and electron) all atoms have protons, neutrons and electrons.

Explanation: atomic nuclei have protons and neutrons, except for hydrogen, the simplest atom whose nucleus is a single proton. Neutrons help the positively charged protons in larger nuclei stay together. Protons and electrons have equal and opposite electric charge and equal numbers in neutral atoms. Atoms with extra or fewer electrons are called ions.

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