An atheist is considered an apostate and is treated like a gentile in almost every respect. I don’t understand rabbis who go and marry such people off. According to Jewish law, one should lower him into a pit and not raise him out.

If anything, it makes more sense that she is not impure to begin with, like a gentile woman. According to many halakhic decisors, she too is considered like a gentile as an apostate.

With God’s help, Rosh Chodesh Cheshvan 5780

To Aleph — greetings,

There is no halakhic decisor who exempts an apostate from the commandments. With regard to obligations that Jews must perform for “your brother” or “your fellow,” there is room to say that one is not obligated toward an apostate, but the apostate is not exempted from his own obligations. Thus, it is permitted to lend to an apostate with interest, but forbidden to borrow from him with interest, since he is bound by the prohibition of lending with interest just like any full Jew.

In any case, nowadays even someone who declares that he is an “atheist” is generally someone who never studied and never tasted the flavor of genuine faith, or who experienced severe crises that caused him to lose his faith, and he is considered inadvertent or coerced. Perhaps his commandment-act does not take effect because he lacks intent, and “one who is coerced is not regarded as one who acted,” but one who sins inadvertently is not considered an apostate.

With blessings, S.Tz.