Beginner Topic 617 of 1102 Inorganic Chemistry
Isotopes of Hydrogen
Protium, deuterium and tritium have zero, one and two neutrons respectively.
In-depth explanation of Isotopes of Hydrogen
Hydrogen has three isotopes that differ only in neutron number: protium, 1H, with no neutron, makes up about 99.98 percent of natural hydrogen, deuterium, D, with one neutron, about 0.015 percent, and tritium, T, with two neutrons, is radioactive with a half-life of about 12.3 years. Because the nuclear mass doubles from H to D, isotope effects are unusually large. Bonds to deuterium have a lower zero-point vibrational energy, so C-D bonds react more slowly than C-H bonds, which is the kinetic isotope effect. Deuterium does not appear in a standard 1H NMR spectrum, so deuterated solvents are used for NMR work. Tritium is used in luminous markers and as a fusion fuel.
Going deeper: Isotopes of Hydrogen
Key ideas: Protium, deuterium and tritium have mass numbers 1, 2 and 3 with 0, 1 and 2 neutrons. Natural abundance of deuterium is about 0.015 percent. Tritium is radioactive with half-life about 12.3 years and emits weak beta particles. Because mass ratios are largest for hydrogen (2 to 1), isotope effects on bond strength and reaction rate are far bigger than for heavier elements, so C-D bonds break more slowly than C-H.
Common mistakes and connections: A common error is to say isotopes differ in chemical properties because of different electrons; they have identical electron configurations and differ mainly in rate and equilibrium by small amounts. Another is mixing mass number and atomic number. Links to heavy water, kinetic isotope effect and NMR solvents like CDCl3.
Visualization of Isotopes of Hydrogen
Atomic masses of the three hydrogen isotopes: each added neutron adds about one unit, so the mass doubles from H to D and the isotope effect is large. The interactive lesson shows this as a live animation or chart.
Worked example and use case
Deuterated chloroform, CDCl3, is an NMR solvent that does not swamp the proton signals.
Frequently asked questions about Isotopes of Hydrogen
What is Isotopes of Hydrogen?
Protium, deuterium and tritium have zero, one and two neutrons respectively.
Is Isotopes of Hydrogen a beginner, intermediate or advanced topic?
Isotopes of Hydrogen is a beginner topic in Inorganic Chemistry. It needs no earlier chemistry lessons and is a good starting point.
What should I learn before Isotopes of Hydrogen?
Study these earlier topics in Inorganic Chemistry first: Hydrogen.
What comes after Isotopes of Hydrogen?
The next topics in Inorganic Chemistry are Hydrides and Water Chemistry.
Can I practise Isotopes of Hydrogen with quizzes?
Yes. The interactive lesson includes a self-check question on Isotopes of Hydrogen, and the Inorganic Chemistry quiz draws on every topic in this area.
Where Isotopes of Hydrogen fits in Inorganic Chemistry
Isotopes of Hydrogen is topic 2 of 113 in Inorganic Chemistry.