Introduction of Deuteron Mass
An atom which consists of particles too small are known as subatomic particles. One of the subatomic particles is known as deuteron.
In Vedantu, this comprehensive section of the Physics chapter explains about deuteron and its mass. The website provides easy downloadable pdfs to the students for them to understand the definition of deuteron mass, how to determine its value and note the important difference between deuteron and deuterium.
What is a Deuteron?
The deuteron is a subatomic particle that contains a neutron and a proton. The atom is called deuterium, and the nucleus which exists in it is called a deuteron. It is one of the two stable isotopes of hydrogen. It is a stable particle due to the presence of the same number of neutrons and protons. Because of which, deuterium is positively charged. The free neutron of the deuterium atom is unstable and hence it usually undergoes beta decay with a half-life period of around 10.3 minutes.
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Binding energy is defined as the amount of energy needed to split a particle from a system of particles or to disperse the entire particles of the system. The binding energy of deuteron is approximately equal to 2.2 MeV. During the process of beta decay, change in energy occurs inside the atom. If the free neutron of the deuterium undergoes beta decay to form a proton, an electron, and an antineutrino, the total mass-energy of the constituent particles will be:
2(938.27 MeV) + 0.511 MeV = 1877.05 MeV
However, the energy of a deuteron particle is 1875.6 MeV, which means that it is stable against beta decay in terms of energy. During beta decay, the free neutron produces energy of 0.78 MeV, but the deuteron that has the binding energy of 2.2 MeV prevents the decay of the neutrons.
Deuterium Explained
Deuterium or hydrogen-2, symbol D, is also known as heavy hydrogen. There are two stable isotopes of hydrogen; one is protium or hydrogen-1 and the other is deuterium or hydrogen-2. The nucleus of deuterium is called a deuteron which contains a proton and a neutron, whereas the protium doesn't contain any neutron in its nucleus. Deuterium is abundantly available in the oceans, one deuterium atom is found per 6420 atoms of hydrogen.
Did You know?
The stability of the deuterium atom has played a major role during the formation of the universe in the initial stage. In the Big Bang model it is assumed that the number of protons and neutrons are equal. In the early stages the available energies were much higher as compared to 0.78 MeV required to convert an electron and a proton into a neutron. When the temperature dropped, the neutrons were no longer generated from the protons. The decay of neutrons gradually decreased the number of neutrons. The neutrons which combined with the protons and formed the deuteron didn't undergo any further decay. If all the neutrons had decayed, the universe wouldn't be as we know it.
Deuteron Mass and Charge
Deuterium is a stable atomic particle containing a proton and neutron. It is denoted by D or 2H and is called Hydrogen-2. Mass of deuteron is expressed in terms of an atomic mass unit (amu) or electron volts (eV). The Charge of deuteron is +1e. This is due to the presence of protons.
1 Amu in Mev
The atomic mass unit (amu) is defined as the 1/12 mass of a carbon-12 atom. The carbon-12 or C-12 atom consists of 6 neutrons and 6 protons in its nucleus. Precisely, one amu is the average mass proton and neutron at rest.
If we want to convert the binding energy in terms of MeV (mega electron volt) per nucleon, will have to apply the conversion factor which is given by
1 MeV = 1.602 x 10-13 J
One amu is equivalent to energy of 931.5 MeV.
Amu Value
One AMU is the average of the rest mass of a neutron and the rest mass of a proton. This mass is approximately equal to 1.67377 x 10-27 kilogram (kg), or 1.67377 x 10-24 gram (g). The mass of an atomic particle in terms of amu is approximately equal to the number of protons and neutrons in its nucleus.
MeV Meaning
MeV is the abbreviation for mega- electron volt, and mev is the abbreviation for million electron volts.
A MeV or Mega electron-volt is 1 million times of an eV. One eV (electron-volt) is defined as the energy gained by an electron (or any other charged particle having a charge equal to that of an electron) when it passes through a potential difference of 1 volt. In SI unit 1eV is equal to 1.6*10-19 Joules.
Mass of a Deuteron
The exact formula applied to determine the mass of a deuteron is through atomic mass unit or mass electron volt is as follows:
To determine the mass of a deuteron, it is calculated by using the atomic mass unit (amu) or Mass electron volts (MeV). The one by twelfth part of the mass of a carbon 12 atom is defined as an atomic mass unit. Basically, there are equal amounts of neutrons and protons, six and six each, in the nucleus of the carbon 12 atom.
One atomic mass unit (amu) is the average of the proton and neutron rest mass. To calculate the atomic mass unit of any deuteron mass, the formula shown below is applicable to it. The equations differ with the amount of mass density in the atomic structure of the atom. Thus, the atomic mass value is defined in the following way.
FAQs on Deuteron Mass
1. What is a deuteron and how is it different from a deuterium atom?
A deuteron is the nucleus of a deuterium atom, consisting of one proton and one neutron bound together. Deuterium, on the other hand, is the entire atom, which includes the deuteron as its nucleus plus one orbiting electron. Key differences are:
- Composition: A deuteron is just a proton and a neutron (2H+), while a deuterium atom (2H or D) is a proton, a neutron, and an electron.
- Charge: A deuteron has a net positive charge of +1e, whereas a deuterium atom is electrically neutral.
- Identity: The deuteron is a nucleus, while deuterium is a stable isotope of the element hydrogen.
2. What are the standard values for the mass and charge of a deuteron?
The mass and charge of a deuteron are fundamental properties in nuclear physics. The standard accepted values are:
- Mass: The mass of a deuteron can be expressed in several units:
- In atomic mass units (amu): 2.014102 u
- In kilograms (kg): 3.343583 × 10-27 kg
- In mega-electron volts (MeV/c²): 1875.61 MeV/c²
- Charge: As it contains one proton and no electrons, the charge of a deuteron is +1e, which is equal to +1.602 × 10-19 Coulombs.
3. What are the mass number and atomic number for a deuteron?
For a deuteron, the key nuclear numbers are:
- The atomic number (Z) is 1. This is because it contains one proton, which defines it as a form of hydrogen.
- The mass number (A) is 2. This is the total count of nucleons (protons + neutrons), which is 1 + 1 = 2.
4. Why is the mass of a deuteron slightly less than the combined mass of a separate proton and neutron?
This phenomenon is known as mass defect. When a proton and a neutron bind together to form a deuteron, a small amount of their total mass is converted into energy. This released energy is the binding energy that holds the nucleus together. According to Einstein's mass-energy equivalence principle (E=mc²), this loss in mass (Δm) is directly proportional to the binding energy (Eb) that stabilises the deuteron. Therefore, a stable deuteron has less mass than its individual constituent particles when they are free.
5. What is the significance of the deuteron's binding energy in understanding nuclear physics?
The deuteron's binding energy (approximately 2.22 MeV) is highly significant for several reasons:
- Model for Nuclear Force: As the simplest bound system of two nucleons (a proton and a neutron), the deuteron is a fundamental model for studying the properties of the strong nuclear force.
- Nuclear Stability: The binding energy explains why the deuteron is stable. While a free neutron decays, the neutron inside a deuteron is stable because the energy required to break the nucleus apart (2.22 MeV) is greater than the energy released by neutron decay (0.78 MeV).
- Stellar Nucleosynthesis: The formation of deuterons was a critical first step in the creation of heavier elements in the early universe and inside stars.
6. How does the mass of a deuteron compare to that of a single proton or neutron?
A deuteron's mass is nearly twice the mass of a proton, but the comparison reveals key physics concepts. Here's a breakdown:
- Proton Mass: ~1.007276 u
- Neutron Mass: ~1.008665 u
- Deuteron Mass: ~2.014102 u
If you simply add the mass of a free proton and a free neutron, you get ~2.015941 u. The deuteron's actual mass is slightly less than this sum due to the mass defect, where the difference is converted into the nuclear binding energy that holds them together.
7. If a deuteron is made of a proton and a neutron, why isn't it considered a form of helium?
This is a common point of confusion. An element's identity in the periodic table is determined solely by its atomic number (Z), which is the number of protons in its nucleus.
- A deuteron has one proton (Z=1), which by definition makes it an isotope of hydrogen.
- Helium (He) is defined by having two protons (Z=2).
The number of neutrons only determines the isotope of that element (e.g., protium, deuterium, tritium are all isotopes of hydrogen), not the element itself.
