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What is Protium?

Protium is the basic hydrogen atom with a single proton circled by a single electron.

An isotope of an element is defined as an atom that has a similar number of protons but with a differential number of neutrons. Protium is given as the regular version of hydrogen and can be represented by the letter-H. Protium also contains one proton and zero neutrons. At the same time, deuterium contains one neutron and one proton – unlike the common hydrogen atom, which has one proton, one electron, and zero neutrons.

Protium Symbol

The lighter isotope of hydrogen is referred to as ”protium” but with no chemical symbol other than 1H, which has been assigned to it. Subsequently to the deuterium discovery, the third isotope of hydrogen of the relative mass of order three was found to exist.

Atoms of similar elements can contain different numbers of neutrons; the different possible versions of every element are referred to as isotopes. The numbers of both protons and electrons are similar for every isotope because they define the element, including its chemical behaviour.

The element symbol of an isotope is given as:



Z = number of protons = number of electrons = atomic number

A = number of protons + number of neutrons = mass number

The shorthand writing for the isotopes protium of element symbol is


Protium Structure

Protium is the most common isotope of hydrogen, which is also called a hydrogen atom. A hydrogen atom is defined as an atom of the chemical element hydrogen. The electrically neutral atom consists of a single positively-charged proton and a single negatively-charged electron, which are bound to the nucleus by the coulomb force. The most abundant isotope is given as protium, hydrogen-1, or light hydrogen contains zero neutrons, and other isotopes of hydrogen such as deuterium contain either one or more neutrons.

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Protium on the Periodic Table

Hydrogen has been placed along with the elements of group 1 in the long form of the periodic table also, but it is separated slightly to indicate its distinctive character and thereby to confirm the views of the Mendeleev.

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Protium can be represented using the symbol H. The atomic number of protium is given as one and the protium mass number is given as 1. It also contains one electron in its 1s orbital and one proton in its nucleus. And, the naturally occurring hydrogen holds 99.985% of this isotope.

Hydrogen isotopes occupy the same and exact position in the periodic table because all of them hold one proton each. Their chemical behaviour is the same because of the similar electronic configuration. However, they vary in the physical properties, which are mass-dependent.

Atomic and Physical Properties of Protium

A few atomic and physical properties of the three isotopes can be given as follows:



Melting point/K


Boiling point/K


Relative atomic mass/g mol-1


Enthalpy of vaporization /kJ mol-1


Enthalpy of fusion /kJ mol-1


Density /g L-1


Critical pressure/bar


Critical temperature/K


Nuclear spin quantum number


Enthalpy of dissociation/kJ mol-1


Protons vs. Protium

As the name at times, protium is used for hydrogen molecules or atoms in which the nuclei are protons - hydrogen-1, to provide it with another name. This is to differentiate it from deuterium, which contains atoms with a nucleus consisting of hydrogen-2, a proton, and neutron. (Or tritium, the hydrogen-3 with two neutrons, but tritium is radioactive too)

Protons are defined as the hydrogen nuclei without the attached electron.

Finding Protons

Protons and neutrons (which are collectively known as nucleons) are found in the nuclei. On Earth, they are found in the complex nuclei form, for example, Carbon with six protons and six neutrons. These nuclei were created in the previous generations of stars, where the Sun is likely in the third generation of stars (confusingly known as a Population 1 star). The debris cloud’s heavier elements that formed the Sun are what became planets.

Only about 5 per cent of the galaxy’s mass is in stars, with the rest in gas clouds and others in non-collapsed structures. Primarily, this gas is molecular hydrogen or atomic, meaning that most of the nucleons present in the Universe are isolated protons. All in, about 70 percent of the nucleons in the Universe are present in hydrogen.

Referring Protium

Protium can refer to:

  • Hydrogen-1 or Protium (isotope), which is the most common isotope of hydrogen element, having one proton, one electron, and zero neutrons

  • Protium (plant), which is a genus of chiefly tropical American trees present in the family Burseraceae, having the fragrant wood

  • Cadence Protium, which is a hardware-accelerated prototyping platform for early software development by the Cadence Design Systems

Uses of Protium

  • Protium contains pantoprazole, which is given as an active ingredient.

  • Protium is also a selective “proton pump inhibitor,” which is a medication that reduces the produced amount of stomach acid.

  • It can be used to treat intestine and stomach acid-related illnesses.

FAQ (Frequently Asked Questions)

Q1. Why is Protium Considered as Most Abundant?

Answer: The most common isotope of hydrogen is given as H (with the atomic mass of 1.007825032241 (94) u) with an abundance of over 99.98 per cent. Because the isotope’s nucleus consists of only one proton, there is formal name protium. The proton was never observed to decay, and therefore, hydrogen-1 is considered as a stable isotope.

Q2. Where is Protium Found?

Answer: A total abundance in the oceans of ~156.25 ppm, accounts for up to 0.0156 percent of all the hydrogen that is present on Earth. The deuterium nucleus, which is called a deuteron, holds one proton and one neutron (with the mass number as 2), whereas the far more popular isotope of the hydrogen, the protium, has zero neutrons in the nucleus.

Q3. Where Does Tritium Come From?

Answer: Tritium is described as a radioactive type of hydrogen that exists naturally, formed in the atmosphere when the cosmic rays interfere with air molecules. Thus, tritium exists worldwide in trace or very low concentrations in groundwater. This is also explained as a by-product of the nuclear power plants that produce electricity.

Q4. Is Protium an Isotope?

Answer: The atomic mass of Protium (otherwise called hydrogen-1) is given as 1.00782504, which is considered as a stable isotope. This possesses one proton and zero neutrons. At times, ordinary hydrogen is called protium. Since the deuterium nucleus is twice as heavy as that of the protium, deuterium is also referred to as ‘super hydrogen.