Question

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Answer 1

What is the thing in the nucleus supposed to be?

Answer 2

So, it means one proton and one neutron?

Answer 3

Or two protons and neutrons? It's not clear.

Answer 4

;-;
Then, there's not enough information I guess. It can be 2 of your 4 answer choices.

Answer 5

Just in case, it'll be either C or D. A hydrogen atom has 1 proton, neutron, and electron, which can be shown here.
And a helium ion has 2 protons and neutrons, but only 1 electron, which can also be shown here. An ion is an atom that doesn't have the same number of electrons as it does protons.

Answer 6

D. hydrogen atom