What is "hydrogen has three isotopes 1h?

Hydrogen has three isotopes: 1H, 2H, and 3H. 1H is the most abundant and stable isotope of hydrogen, consisting of a single proton and no neutron in its nucleus. 2H, also known as deuterium, has one neutron in addition to its proton, making it heavier and less abundant than 1H. 3H, also known as tritium, has two neutrons in addition to its proton, making it even heavier and extremely rare in nature. Tritium is also radioactive and has a half-life of about 12 years, which can potentially make it hazardous to living organisms. Hydrogen isotopes have different properties and uses, such as deuterium being used as a fuel for nuclear reactors and tritium being used in nuclear weapons and experimental fusion reactors.