# Chapter 2 Atoms, Molecules, and Ions - 2-2 Atomic Number and Atomic Mass - Review & Check for Section 2-2 - Page 48: 1

B

#### Work Step by Step

According to the periodic table, Mn has 25 protons. With a mass of 54.9380u, and the masses of the proton and neutron being 1.007276u and 1.008665u respectively: $54.9380=25\times1.007276+n^0\times1.008665$ $n^0=29.5\approx30$

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