ConstantID

Alpha particle molar mass

Atomic & nuclearMeasured

M(α) = 4.001 506 1833(12) × 10−3 kg mol−1

Value
4.001 506 1833 × 10−3 kg mol−1
Standard uncertainty
1.2 × 10−12 kg mol−1
Relative uncertainty
3.0 × 10−10 (300 parts per trillion)
Status
Measured
Symbol
M(α)
Source
CODATA 2022 via NIST · NIST entry

Use in a calculation

# alpha particle molar mass, CODATA 2022 (NIST)
alpha_particle_molar_mass = 4.0015061833e-3  # kg mol^-1, standard uncertainty 1.2e-12

# SciPy: scipy.constants.physical_constants['alpha particle molar mass']

What it is

The mass of one mole of alpha particles (alpha particle), in kilograms per mole.

How the value changed, 1998–2022

Each point is one CODATA adjustment, plotted as its difference from the 2022 value; the bars show one standard uncertainty (an arrowhead means the bar runs off the chart).

alpha particle molar mass: CODATA values 1998–2022 relative to the 2022 value, in parts per billion, with one-standard-uncertainty bars−4−20+2+4parts per billion1998200220062010201420182022

Relative uncertainty

alpha particle molar mass: relative standard uncertainty in each CODATA adjustment, logarithmic scale10⁻¹¹10⁻¹⁰10⁻⁹1998200220062010201420182022
CODATAValue (uncertainty)Relative uncertaintyChange from previous
20224.001 506 1833(12) × 10−33.0 × 10−10 +4.7 σ of 2018
20184.001 506 1777(12) × 10−33.0 × 10−10 −22.7 σ of 2014
20144.001 506 179 127(63) × 10−31.6 × 10−11 +0.0 σ of 2010
20104.001 506 179 125(62) × 10−31.5 × 10−11 −0.0 σ of 2006
20064.001 506 179 127(62) × 10−31.5 × 10−11 −0.4 σ of 2002
20024.001 506 179 149(56) × 10−31.4 × 10−11 +4.4 σ of 1998
19984.001 506 1747(10) × 10−32.5 × 10−10

“Change from previous” is the shift in the value divided by the standard uncertainty of the previous adjustment. Earlier values are converted into the current unit where NIST changed it (for example J s to J Hz⁻¹).

Related constants

Atomic & nuclear mα/me Alpha particle-electron mass ratio 7294.299 541 71(17) Atomic & nuclear mα Alpha particle mass 6.644 657 3450(21) × 10−27 kg Atomic & nuclear mαc2 Alpha particle mass energy equivalent 5.971 920 1997(19) × 10−10 J Atomic & nuclear mαc2 Alpha particle mass energy equivalent in MeV 3727.379 4118(12) MeV Atomic & nuclear mα Alpha particle mass in u 4.001 506 179 129(62) u Atomic & nuclear mα/mp Alpha particle-proton mass ratio 3.972 599 690 252(70) Atomic & nuclear Ar(α) Alpha particle relative atomic mass 4.001 506 179 129(62) Atomic & nuclear rα Alpha particle rms charge radius 1.6785(21) × 10−15 m