Please read the notes following the table.
| Quantity | Value |
|---|---|
| speed of light in a vacuum (c) | 2.99792458E+08 m/s (exact) |
| permeability of a vacuum (µ0) | 4π×1.0E-07 H/m |
| permittivity of a vacuum (ε0) | 8.854187817...E-12 F/m |
| elementary charge (of proton) | 1.60217733(49)E-19 C |
| gravitational constant | 6.67259(85)E-11 Nm2kg-2 |
| unified atomic mass constant (mu = mass 12C / 12) | 1.6605402(10)E-27 kg |
| rest mass of electron (me) | 9.1093897(54)E-31 kg |
| 5.48579903(13)E-04 amu | |
| rest mass of proton (mp) | 1.6726231(10)E-27 kg |
| 1.007276470(12) amu | |
| 1836.152701(37) me | |
| rest mass of neutron (mn) | 1.6749286(10)E-27 kg |
| 1.008664904(14) amu | |
| energy equivalence of rest mass of electron | 0.5109906(15) MeV |
| energy equivalence of rest mass of proton | 938.27231(28) MeV |
| energy equivalence of rest mass of neutron | 939.56563(28) MeV |
| electron specific charge (-e/me) | -1.75881962(53)E11 C/kg |
| Planck constant | 6.6260755(40)E-34 Js |
| h/2π | 1.05457266(63)E-34 Js |
| Rydberg constant | 1.0973731534E+07 1/m |
| fine structure constant | 7.29735308(33)E-03 |
| reciprocal fine structure constant | 137.0359895(61) |
| Hartree energy | 4.3597482(26)E-18 J |
| 2.6255000E+06 J/mol | |
| 27.211652 eV | |
| 627.51E+03 Calories/mol (US Calorie) | |
| Bohr radius | 5.29177249(24)E-11 m |
| electron radius | 2.81794092(38)E-15 m |
| Compton wavelength of electron | 2.42631058(22)E-12 m |
| Compton wavelength of proton | 1.32141002(12)E-15 m |
| Compton wavelength of neutron | 1.31959110(12)E-15 m |
| Avogadro constant (NA, L) | 6.0221367(36)E+23 1/mol |
| Faraday constant | 9.6485309(29)E+04 C/mol |
| molar gas constant | 8.314510(70) J/K/mol |
| Boltzman constant | 1.380658(12)E-23 J/K |
| Stefan-Boltzman constant | 5.67051(19)E-08 W/m2K-4 |
| first radiation constant | 3.7417749(22)E-16 Jm2s-1 |
| second radiation constant | 1.438769(12)E-02 mK |
| Bohr magneton | 9.2740154(31)E-24 J/T |
| nuclear magneton | 5.0507866(17)E-27 J/T |
| magnetic flux quantum | 2.06783461(61)E-15 Vs |
| gyromagnetic ratio of proton | 2.67522128(81)E+08 1/s/T |
| *1/2π | 4.2577469(13)E+07 Hz/T |
| in pure water | 2.67515255(81)E+08 1/s/T |
| *1/2π | 4.2756375(13)E+07 Hz/T |
| magnetic moment of electron | 9.2847701(31)E-24 J/T |
| in terms of Bohr magneton | 1.001159652(10) |
| magnetic moment of proton | 1.41060761(47)E-26 J/T |
| in terms of Bohr magneton | 1.521032202(15)E+03 |
| in pure water | 1.520993129(17)E+03 |
| in terms of nuclear magneton | 2.792847386(63) |
| Electronvolts per mol | 96.485333E+03 J/mol |
| 23.060548E+03 Calories/mol | |
| 1/cm (harmonic oscillator) | 9.93223731E-24 J |
| 5.98132908 J/mol | |
| 8.06554093 E-3 eV | |
| Calorie (USA - definition) | 4.18400 J |
| Mean Calorie | 4.19002 J |
| 15 deg C Calorie | 4.1890 J |
| 220 lattice parameter of silicon (d220 = a/80.5) | 1.92015540(40)E-13 |
Notes
The amu (chemical scale) was one-sixteenth of the average mass of oxygen atoms as found in nature. 1 u = 1.000 317 9 amu (physical scale) = 1.000 043 amu (chemical scale) WHILE MASS OF AN ELECTRON. The mass of electron in grams = 9.10938356 x 10-28 The mass of electron in Atomic Mass Unit = 5.4858 x 10 -4 How Mass of Electron Calculated The mass of an electron is calculated by the mass to charge ratio.
The above values are taken from Refs. [1-3]: these are good enough for most purposes. Recently new values have been published which are considerably more accurate, except for the gravitational constant, G. For details of these please see Ref. [4] and the NIST website.
References
- E. R. Cohen and B. N. Taylor, 'The 1986 CODATA recommended values of the fundamental physical constants.', J. Res. National Bureau of Standards, 92(2), 85-95 (1987).
- E. R. Cohen and B. N. Taylor, 'The 1986 adjustment of the fundamental physical constants', CODATA Bulletin Number 63, (1986); and Rev. Mod. Phys., 59(4), 1121-1148 (1987).
- CRC Handbook of Chemistry and Physics, 58th edition (1977-78).
- P. J. Mohr and B. N. Taylor, 'CODATA recommended values of the fundamental physical constants: 1998', J. Phys. Chem. Ref. Data, 28(6) (1999); and Rev. Mod. Phys., 72(2), 1713-1852, (2000).
The number in parenthesis after each value is the estimated standard deviation uncertainty of the last digit quoted.
Other Sources of Information:
Any constants missing that you think should be here? Please let us know - thanks!
Last modified: Tue Nov 18 16:00:08 GMT 2003Chris Latham, Chris Ewels.
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Learning Objectives
- Describe the locations, charges, and masses of the three main subatomic particles.
- Determine the number of protons and electrons in an atom.
- Define atomic mass unit (amu).
Dalton's Atomic Theory explained a lot about matter, chemicals, and chemical reactions. Nevertheless, it was not entirely accurate, because contrary to what Dalton believed, atoms can, in fact, be broken apart into smaller subunits or subatomic particles. We have been talking about the electron in great detail, but there are two other particles of interest to us: protons and neutrons. We already learned that J. J. Thomson discovered a negatively charged particle, called the electron. Rutherford proposed that these electrons orbit a positive nucleus. In subsequent experiments, he found that there is a smaller positively charged particle in the nucleus which is called a proton. There is also a third subatomic particle, known as a neutron.
Electrons
Electrons are one of three main types of particles that make up atoms. Unlike protons and neutrons, which consist of smaller, simpler particles, electrons are fundamental particles that do not consist of smaller particles. They are a type of fundamental particles called leptons. All leptons have an electric charge of (-1) or (0). Electrons are extremely small. The mass of an electron is only about 1/2000 the mass of a proton or neutron, so electrons contribute virtually nothing to the total mass of an atom. Electrons have an electric charge of (-1), which is equal but opposite to the charge of a proton, which is (+1). All atoms have the same number of electrons as protons, so the positive and negative charges 'cancel out', making atoms electrically neutral.
Unlike protons and neutrons, which are located inside the nucleus at the center of the atom, electrons are found outside the nucleus. Because opposite electric charges attract each other, negative electrons are attracted to the positive nucleus. This force of attraction keeps electrons constantly moving through the otherwise empty space around the nucleus. The figure below is a common way to represent the structure of an atom. It shows the electron as a particle orbiting the nucleus, similar to the way that planets orbit the sun. This is however, an incorrect perspective, as quantum mechanics demonstrates that electrons are more complicated.
Protons
A proton is one of three main particles that make up the atom. Protons are found in the nucleus of the atom. This is a tiny, dense region at the center of the atom. Protons have a positive electrical charge of one (left( +1 right)) and a mass of 1 atomic mass unit (left( text{amu} right)), which is about (1.67 times 10^{-27}) kilograms. Together with neutrons, they make up virtually all of the mass of an atom.
Neutrons
Atoms of all elements—except for most atoms of hydrogen—have neutrons in their nucleus. Unlike protons and electrons, which are electrically charged, neutrons have no charge—they are electrically neutral. That's why the neutrons in the diagram above are labeled (n^0). The zero stands for 'zero charge'. The mass of a neutron is slightly greater than the mass of a proton, which is 1 atomic mass unit (left( text{amu} right)). (An atomic mass unit equals about (1.67 times 10^{-27}) kilograms.) A neutron also has about the same diameter as a proton, or (1.7 times 10^{-15}) meters.
As you might have already guessed from its name, the neutron is neutral. In other words, it has no charge whatsoever and is therefore neither attracted to nor repelled from other objects. Neutrons are in every atom (with one exception), and they are bound together with other neutrons and protons in the atomic nucleus.
Before we move on, we must discuss how the different types of subatomic particles interact with each other. When it comes to neutrons, the answer is obvious. Since neutrons are neither attracted to nor repelled from objects, they don't really interact with protons or electrons (beyond being bound into the nucleus with the protons).
Even though electrons, protons, and neutrons are all types of subatomic particles, they are not all the same size. When you compare the masses of electrons, protons, and neutrons, what you find is that electrons have an extremely small mass, compared to either protons or neutrons. On the other hand, the masses of protons and neutrons are fairly similar, although technically, the mass of a neutron is slightly larger than the mass of a proton. Because protons and neutrons are so much more massive than electrons, almost all of the mass of any atom comes from the nucleus, which contains all of the neutrons and protons.
| Particle | Symbol | Mass (amu) | Relative Mass (proton = 1) | Relative Charge | Location |
|---|---|---|---|---|---|
| proton | p+ | 1 | 1 | +1 | inside the nucleus |
| electron | e− | 5.45 × 10−4 | 0.00055 | −1 | outside the nucleus |
| neutron | n0 | 1 | 1 | 0 | inside the nucleus |
Table (PageIndex{1}) gives the properties and locations of electrons, protons, and neutrons. The third column shows the masses of the three subatomic particles in 'atomic mass units.' An atomic mass unit ((text{amu})) is defined as one-twelfth of the mass of a carbon-12 atom. Atomic mass units ((text{amu})) are useful, because, as you can see, the mass of a proton and the mass of a neutron are almost exactly (1) in this unit system.
Mass Of One Electron In Amu
Negative and positive charges of equal magnitude cancel each other out. This means that the negative charge on an electron perfectly balances the positive charge on the proton. In other words, a neutral atom must have exactly one electron for every proton. If a neutral atom has 1 proton, it must have 1 electron. If a neutral atom has 2 protons, it must have 2 electrons. If a neutral atom has 10 protons, it must have 10 electrons. You get the idea. In order to be neutral, an atom must have the same number of electrons and protons.
Summary
- Electrons are a type of subatomic particle with a negative charge.
- Protons are a type of subatomic particle with a positive charge. Protons are bound together in an atom's nucleus as a result of the strong nuclear force.
- Neutrons are a type of subatomic particle with no charge (they are neutral). Like protons, neutrons are bound into the atom's nucleus as a result of the strong nuclear force.
- Protons and neutrons have approximately the same mass, but they are both much more massive than electrons (approximately 2,000 times as massive as an electron).
- The positive charge on a proton is equal in magnitude to the negative charge on an electron. As a result, a neutral atom must have an equal number of protons and electrons.
- The atomic mass unit (amu) is a unit of mass equal to one-twelfth the mass of a carbon-12 atom
Contributions & Attributions
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What Is Mass Of Electron In Amu
CK-12 Foundation by Sharon Bewick, Richard Parsons, Therese Forsythe, Shonna Robinson, and Jean Dupon.
Marisa Alviar-Agnew (Sacramento City College)
Henry Agnew (UC Davis)