Is zakat obligatory on inherited money that has not yet been divided, and is zakat obligatory on the land that the mother purchased with this money, and are the heirs sinful for not dividing the inheritance, and how should this money be divided according to Sharia?

The general rule is that the inheritance is divided after death. However, there is no religious impediment to delaying the division for a valid reason and with the consent of the heirs. All of the deceased's properties are considered part of the inheritance. Zakat becomes obligatory upon each heir whose share of the inheritance reaches the nisab (minimum threshold) for zakat, either by itself or when combined with other possessions (cash or trade goods) after a full year (hawl) has passed. As for anyone whose share does not reach the nisab, there is no zakat due on them. Zakat is obligatory on the heir's share, not on the total inheritance. There is no zakat on purchased land unless it was acquired with the intention of trade. The mother's share of the inheritance is one-eighth. What remains is divided among the sons and daughters, with the male receiving the share of two females. It is preferable to refer inheritance matters to Sharia courts to ensure that all rights, debts, and bequests are duly observed.