en.wikipedia.org/wiki/Atom
4 corrections found
The electron is the least massive of these particles by four orders of magnitude
This overstates the mass gap. The proton is about 1,836 times heavier than the electron, so the difference is a bit over 3 orders of magnitude, not 4.
Full reasoning
Using current NIST CODATA values, the electron mass is 9.1093837139 × 10^-31 kg and the proton mass is 1.67262192595 × 10^-27 kg. Dividing these gives a proton-to-electron mass ratio of about 1836.
A factor of 1836 corresponds to a little over 10^3, i.e. about 3.26 orders of magnitude. "Four orders of magnitude" would imply a factor on the order of 10,000, which is much larger than the actual ratio.
So the electron is indeed far lighter than the proton and neutron, but not by four orders of magnitude.
2 sources
- CODATA Value: electron mass
electron mass Numerical value 9.109 383 7139 x 10^-31 kg
- CODATA Value: proton mass
proton mass Numerical value 1.672 621 925 95 x 10^-27 kg
which is in fact true for all of them if one takes isotopes into account.
This is incorrect. Even for individual isotopes, atomic masses are not exact whole-number multiples of hydrogen’s mass; precise measurements show systematic deviations caused by nuclear binding energy.
Full reasoning
Prout's hypothesis proposed that atomic weights should be whole-number multiples of hydrogen's mass. Modern isotope measurements do not make that statement exactly true.
Authoritative sources directly say so. A PubMed-indexed historical review of isotope mass measurements states that after the isotope problem was settled, "more accurate mass measurements showed that even isotopic weights differed to some extent from the whole numbers."
NIST's isotope tables show the mismatch numerically. For hydrogen, the mass of ¹H is 1.00782503223 u. For carbon, the mass of ¹²C is 12.0000000 u exactly. If Prout's idea were "in fact true" for isotopes, carbon-12 would have to equal 12 times the mass of hydrogen-1. But 12 × 1.00782503223 u = 12.09390038676 u, not 12.0000000 u. So isotopic masses are only approximately related to small whole numbers, not exactly equal to whole-number multiples of hydrogen.
The reason is the nuclear mass defect: binding energy changes the mass of a bound nucleus, so isotope masses are not exact sums of hydrogen-mass units.
3 sources
- Mass spectrometry and isotopes: a century of research and discussion - PubMed
The isotope problem was finally settled, but more accurate mass measurements showed that even isotopic weights differed to some extent from the whole numbers.
- Atomic Weights and Isotopic Compositions for Hydrogen
1 H 1 1.00782503223(9) 0.999885(70) [1.00784,1.00811]
- Atomic Weights and Isotopic Compositions for Carbon
6 C 12 12.0000000(00) 0.9893(8) [12.0096,12.0116]
a mole of carbon-12 atoms weighs exactly 0.012 kg.
This is outdated under the current SI. Since the 2019 redefinition of the mole, one mole is defined by an exact Avogadro constant, so the molar mass of carbon-12 is no longer exactly 0.012 kg/mol.
Full reasoning
This statement used to be exactly true under the old SI definition of the mole, but it is no longer exact under the current SI definition adopted in 2019.
The BIPM explains that the earlier definition of the mole specified that the molar mass of carbon-12 should be exactly 0.012 kg/mol. It then states that the present definition instead fixes the numerical value of the Avogadro constant, with the effect that the mole is no longer dependent on the kilogram.
IUPAC states the consequence explicitly: "Because the molar mass of unbound carbon-12, M(12C), is no longer 12 g mol−1 exactly...". So while a carbon-12 atom still has a relative atomic mass of exactly 12 Da, it does not follow anymore that one mole of carbon-12 atoms has a mass of exactly 0.012 kg. It is very close to that value, but not exact in the current SI.
2 sources
- mole - BIPM
Following proposals by the IUPAP, IUPAC and ISO, the CIPM developed a definition of the mole in 1967 and confirmed it in 1969, by specifying that the molar mass of carbon 12 should be exactly 0.012 kg/mol... This has the effect that the new definition of the mole and the value of the Avogadro constant are no longer dependent on the definition of the kilogram.
- Definition of the mole (IUPAC)
Because the molar mass of unbound carbon-12, M(12C), is no longer 12 g mol−1 exactly, the molar mass constant, Mu, is no longer 1 g mol−1 exactly.
Up to 95% of the Milky Way's baryonic matter are concentrated inside stars
This overstates the share of Milky Way baryons locked in stars. Current sources describe a much larger gas-and-dust component, with roughly 6×10^10 solar masses in stars out of about 10^11 solar masses of baryonic matter, and a hot gas halo whose mass is comparable to the stars’ mass.
Full reasoning
The claim that up to 95% of the Milky Way's baryonic matter is inside stars is far too high.
A recent Springer reference entry on the Milky Way says the galaxy has roughly 10^11 solar masses of baryonic matter, with about 6 × 10^10 solar masses in stars and the rest in gas and dust. That puts the stellar share at about 60%, not 95%.
In addition, NASA/Chandra reports that the Milky Way is surrounded by a hot gas halo whose estimated mass is comparable to the mass of all the stars in the galaxy. If that halo mass is included—as it should be when discussing the galaxy's baryonic matter—the fraction in stars is even farther from 95%.
So the article's figure is not just a little outdated; it substantially overestimates how much of the Milky Way's baryonic matter is concentrated in stars.
2 sources
- Milky Way | Springer Nature Link
The Milky Way (MW) is a spiral galaxy with an approximate mass of 1.3 × 10^12 M⊙, where roughly 10^11 M⊙ is baryonic matter (~6 × 10^10 in stars and the rest in gas and dust).
- NASA's Chandra Shows Milky Way is Surrounded by Halo of Hot Gas
The estimated mass of the halo is comparable to the mass of all the stars in the galaxy.