Why doesn't the atomic number change by two in the process of production of Americium?
What might be confusing is that it's actually two reactions. Two neutrons are captured followed by a single beta decay:

$$\ce{^239_94Pu -&gt;[2(n,\gamma)]^241_94Pu-&gt;[\beta^-]^241_95Am}$$

The first reaction leaves the new nucleus in an excited state, so a gamma ray is emitted. The second reaction is actually quite slow with a halflife of ~14 years. It's a beta minus decay so that's why an electron is emitted.