uncombined

I think the latter is more common since you are looking for uncombined atoms.

It is extremely difficult to isolate from any compounds, let alone keep uncombined.

This means that the combustion gases often have both oxygen and fuel remaining uncombined in them.

A series of distinctive but uncombined initials, such as a royal cypher.

A hard, rare metal under standard conditions when uncombined, tungsten is found naturally on Earth only in chemical compounds.

The oxidation state of a free element (uncombined element) is zero.

As a result, platinum is often found chemically uncombined as native platinum.

With respect to metals: the term native state refers to metals which are found chemically uncombined in nature.

Occasionally, however, metals are found in uncombined metallic forms, in varying degrees of purity.

Native element minerals are those elements that occur in nature in uncombined form with a distinct mineral structure.

In fact, the only uncombined metal that has ever appeared on the planet has been the nickel-iron of an occasional meteorite.

Most protons remained uncombined as hydrogen nuclei.

Its uncombined form-you all-is used less frequently.

Particles of uncombined antimatter from the exhaust raged merrily in theHammer 's interior.

It is too reactive to be found uncombined in nature, but when isolated, is relatively stable in dry air at room temperature.

While about 32 of the chemical elements occur on Earth in native uncombined form, most of these occur as mixtures.

They are never found in nature uncombined because they are unstable and they react fast to other elements.

It sometimes occurs free (chemically uncombined) in nature, but is usually found combined with sulfur in the ore stibnite.

It never appears uncombined in nature and almost never stays uncombined for long.

Elemental bismuth may occur naturally uncombined, although its sulfide and oxide form important commercial ores.

Chemically uncombined boron, which is classed as a metalloid, is not found naturally on Earth.

Think of it as the first few moments after the Big Bang, when there is nothing but a soup of uncombined electrons and neutrons.

However, there is no accessible natural reserve of uncombined hydrogen, since what little there is resides in Earth's exosphere.

The "uncombined fatty acids" or "free fatty acids" found in organisms come from the breakdown of a triglyceride.

Platinum is often found chemically uncombined as native platinum and alloyed with iridium as platiniridium.