Isobars are atoms that have same atomic mass but different atomic number. They have different atomic numbers because they have different numbers of protons. They have the same atomic mass because they have just enough neutrons to make the same total of nucleons. Isobars occur at different places in the Periodic Table.
The Holocaust (also called Ha-Shoah in Hebrew) refers to the period from January 30, 1933 - when Adolf Hitler became chancellor of Germany - to May 8, 1945, when the war in Europe officially ended.
The Holocaust was the murder of approximately six million Jews by the Nazis and their collaborators. Between the German invasion of the Soviet Union in the summer of 1941 and the end of the war in Europe in May 1945, Nazi Germany and its accomplices strove to murder every Jew under their domination.