The number of neutrons in a nucleus equals the mass number minus the:

The number of neutrons in a nucleus…

Answer: atomic number.

A atomic number
B electron count
C photon count
D neutron count

Correct answer: A. atomic number

Explanation: Number of neutrons = mass number A − atomic number Z.

Comparison of the Thomson model and the Rutherford model of the atom: in the Thomson plum pudding model alpha particles pass almost straight through a diffuse positive sphere, while in the Rutherford model a concentrated central nucleus deflects some alpha particles through large angles, with the lower panels showing the alpha particle source and gold foil and the observed result of wide-angle scattering

The Geiger–Marsden alpha-scattering result: a few alpha particles bounce back at large angles, which rules out Thomson’s diffuse model and demands a tiny, massive, positively charged nucleus. Image: Kurzon, CC BY 3.0, via Wikimedia Commons.

Concept context

Thomson's plum-pudding model, Rutherford's nuclear model from alpha-scattering, Bohr's postulates and hydrogen spectrum, spectral series (Lyman to Pfund), Rydberg formula, and limitations of each model.

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The number of neutrons in a nucleus equals the mass number minus the:

Concept context

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