Chemistry ExpertPh.D., Biomedical Sciences, university of Tennessee at KnoxvilleB.A., Physics and also Mathematics, Hastings College
Dr. Helmenstine stop a Ph.D. In biomedical sciences and is a science writer, educator, and consultant. She has taught scientific research courses at the high school, college, and graduate levels.

You are watching: How many hydrogen atoms are in a molecule of water

Have you ever wondered how plenty of atoms are in a drop of water or how many molecules room in a solitary droplet? The answer depends on your meaning of thevolume the a droplet that water. Water fall vary significantly in size, for this reason this starting number defines the calculation. The rest of the is a simple chemistry calculation.

Let's usage the volume that a water drop the is supplied by the medical and scientific community. The welcomed average volume the a autumn of water is exactly 0.05 mL (20 drops every milliliter). It transforms out there room over 1.5 sextillion molecules in a drop of water and more than 5 sextillion atoms every droplet.

chemical Formula of Water

To calculate the variety of molecules and also atoms in a water drop, you require to know the chemistry formula the water. There are two atom of hydrogen and also one atom the oxygen in every water molecule, do the formula H2O. So, every molecule of water has 3 atoms.

Molar massive of Water

Determine the molar mass of water. Perform this by adding up the fixed of hydrogen atoms and oxygen atoms in a mole of water by looking increase the atomic mass of hydrogen and also oxygen on theperiodic table. The fixed of hydrogen is 1.008 g/mol and also the mass of oxygen is 16.00 g/mol, therefore the fixed of a mole that water have the right to be calculated together follows:

thickness of Water

Use the density of water to identify the mass of water per unit volume. Thedensity the wateractually different depending on conditions (cold water is denser; heat water is much less dense), however the value typically used in calculations is 1.00 gram per milliliter (1 g/mL). In other words, 1 milliliter the water has actually a massive of 1 gram. A fall of water is 0.05 mL that water, for this reason its mass would be 0.05 grams.

moles that water in one autumn = 0.05 grams x (1 mole/18.016 grams)moles of water in one fall = 0.002775 moles

utilizing Avogrado's Number

Finally, useAvogadro"s number to identify the number of molecules in a autumn of water. Avogadro"s number tells united state there are6.022 x 1023molecules of water per mole of water. So, following we calculate how numerous molecules there space in a drop of water, which we determined contains 0.002775 moles:

molecules in a autumn of water = (6.022 x 1023 molecules/mole) x 0.002275 molesmolecules in a fall of water = 1.67 x 1021 water molecules
atoms in a fall of water = 3 atoms/molecule x 1.67 x 1021 moleculesatoms in a autumn of water = 5.01 x 1021 atoms

atom in a drop of Water vs. Fall in the s

One interesting question is whether over there are an ext atoms in a fall of water 보다 there are drops the water in the ocean. To identify the answer, we require the volume the water in the oceans. Sources estimate this to be in between 1.3 billion km3 and 1.5 km3. I'll usage the USGS (United states Geologic Survey) value of 1.338 billion km3 for the sample calculation, however you deserve to use whichever number you would certainly like.

Now, your answer depends on the size of your drop, so you division this volume by her drop volume (0.05 ml or 0.00005 together or 5.0 x 10-5 l is the average) to gain the number of drops that water in the ocean.

number of drops of water in the ocean = 1.338 x 1021 liters complete volume / 5.0 x 10-5 liters every drop

So, over there are much more drops the water in the ocean than there are atoms in a autumn of water. Exactly how many much more drops depends mostly on the size of her drops, yet there are between 1,000 and 100,000 an ext drops of water in the ocean than atom in a autumn of water.


Gleick, P.H. "Where is Earth"s Water." Earth"s Water Distribution. U.S. Geology Survey, 28August2006.

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Helmenstine, ann Marie, Ph.D. "Calculating the number of Atoms and Molecules in a fall of Water.", Aug. 25, 2020,, ann Marie, Ph.D. (2020, respectable 25). Calculating the number of Atoms and also Molecules in a fall of Water. Retrieved from, ann Marie, Ph.D. "Calculating the variety of Atoms and Molecules in a fall of Water." Https:// (accessed December 17, 2021).