Does a divorce occur and count as one pronouncement, and is expiation obligatory for the husband who swore that his wife would be divorced if she went to work, and the wife went to work while she was menstruating?

The majority of scholars hold that a conditional divorce takes effect upon the fulfillment of the condition. So, if the husband made his wife's divorce conditional on her going out to work, and she did go out, then divorce has occurred according to the majority. The divorce here does not recur with repeated outings if the wording does not imply repetition, such as saying: "If you go." The occurrence of the breach of the oath during menstruation does not prevent the divorce from taking effect, according to the majority. The husband can take back his wife before the completion of the 'iddah (definition) if this divorce does not complete the three divorces. However, according to the view of Ibn Taymiyyah and those who agreed with him, divorce in this case does not occur because it is an unlawful, innovative divorce (طلاق بدعي).