def from_Z(z: int):
        """
        Get an element from an atomic number.

        Args:
            z (int): Atomic number

        Returns:
            Element with atomic number z.
        """
        for sym, data in _pt_data.items():
            if data["Atomic no"] == z:
                return Element(sym)
        raise ValueError("No element with this atomic number %s" % z)