What is "space",(outer space) on the molecular level .?

Question

for example

oxygen- o2

water-h2o

Answer 1

The matter consists of about 99% gas and 1% dust by mass.

Densities range from a few thousand to a few hundred million

particles per cubic meter with an average value in the

Milky Way Galaxy of a million particles per cubic meter.

... the gas is roughly 90% hydrogen and 10% helium by number

of nuclei, with additional heavier elements...in trace amounts.

Wikipedia - Interstellar Medium

Note that inside the heliopause the solar wind dominates the composition of the vacuum.  It is believed that space far from the super clusters and networks of matter that span the Universe is orders of magnitude less dense than in the super clusters.  Dark matter is not accounted for in these estimates. Nor are the vacuum fluctuations.

Answer 2

Outer space itself is almost a perfect vacuum. That means that there  are no gasss. Some very, very light (in terms of density) molecules exist but there isn't that much. For the most part it is a perfect vacuum. Given this, we can't we say what it is like on the molecular level because there aren't any molecules. The only molecules that are there are so "thin" that it is extremely hard to detect them and even harder to analyze.

You'll often here people refer something called "solar winds". These winds aren't winds like we experience on Earth. They are highly charged particles emitted from the sun. This is not wind created by pressure like on Earth. This wind is just a stream of highly charged particles.