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 systematic annihilation of six million Jews by the Nazi regime during World War 2. In 1933 approximately nine million Jews lived in the 21 countries of Europe that would be occupied by Germany during the war. By 1945 two out of every three European Jews had been killed.