molecular weight

American  

noun

Chemistry.

1. the average weight of a molecule of an element or compound measured in units once based on the weight of one hydrogen atom taken as the standard or on 1/16 (0.0625) the weight of an oxygen atom, but after 1961 based on 1/12 (0.083) the weight of the carbon-12 atom; the sum of the atomic weights of all the atoms in a molecule. mol. wt.

---

molecular weight British  

noun

1. the former name for relative molecular mass

---

molecular weight Scientific  

1. The sum of the atomic weights of the atoms contained in a molecule.

2. Also called relative molecular mass

---

molecular weight Cultural  

1. The sum of the atomic weights of all the atoms in a molecule.

---

Etymology

Origin of molecular weight

First recorded in 1875–80

Example Sentences

"To date, it is not well understood how nitrogen molecular ions with large molecular weight can exist at such high altitudes," he continued.

From Science Daily • Dec. 5, 2024

Since the molecular weight of salt is very small, we use a special membrane that filters it through very small holes that allows only these molecules to pass through.

From Salon • Sep. 10, 2024

Additionally, by adjusting the ratios, they can control the degree to which the chitin is processed and can therefore 'fine tune' the molecular weight of the final product.

From Science Daily • Feb. 21, 2024

On a recent day in C2N’s lab, scientist Samantha Koch prepared plasma samples for analysis by mass spectrometers, instruments that identify compounds by molecular weight.

From Washington Post • Nov. 17, 2022

Perhaps there is some major and as yet undiscovered atmospheric constituent—nitrogen, for example—which keeps the average molecular weight of the atmosphere high and prevents blowoff.

From "Cosmos" by Carl Sagan