D2O (heavy water)

D2O, commonly known as heavy water, is a form of water where the hydrogen atoms are replaced with a heavier isotope called deuterium. While regular water (H2O) has hydrogen atoms, heavy water contains two deuterium atoms along with one oxygen atom (D2O). This alteration gives it unique properties, making it useful in nuclear reactors as a neutron moderator and in certain scientific research. Heavy water is not harmful in small quantities, but it can disrupt biological processes in large amounts due to its difference in molecular weight.