Good question! The answer is no--if you took an element out of air, it would NOT still be considered air. So what would it be? Well, that depends where you put it! For example, oxygen is an element that is in air. Some of this oxygen is in the form of water molecules--H₂O. Water, when in the air, is called water vapor. On very cool mornings, sometimes you can see droplets of liquid water form on the surface of car windows and on blades of grass. Where does this water come from? It comes from the air! When the temperature is cold, water molecules in the air all come together to form a liquid. So in this case, when you take the elements of water (H and O) out of the air, they are no longer considered air; because once they come together as droplets they are considered liquid water. Sometimes elements from the air can also combine with solids, and in these cases the element is considered as part of the solid.

In summary, elements can be in one of three phases--gas (like air), liquid, and solid. An element can move from one phase to another, and is considered a gas, liquid, or solid, depending on which state it is in at the moment, even if it had originally come from a different state.

What an interesting question!Lets think about this for a bit. As you clearly already know, air is a mixture of gases that surrounds the earth. Because it contains a mixture of different gases, it also contains many different elements. Some of the elements are present in a pure form. For example, the air is mostly nitrogen, in the form of N₂, with a lot of oxygen (O₂) for us to breathe, and a very little argon (Ar), helium (He), and other such elements. In addition, many elements are present combined with other elements in more mixed-up gas molecules. For example, the air also contains carbon dioxide (CO₂), methane (CH₄), and water (H₂O).

You were probably already aware of most of this, as you probably learned about this in class. Now, lets think about some other things you might already know to see if we can figure out the answer to your question that way. Sometimes the air outside is very dry, but other times it is a lot more wet and humid. This means that sometimes it contains more water molecules than at other times. There is a lot of concern right now about the amount of carbon dioxide that is being put into the air when we burn coal and gas, and plants take carbon dioxide out of the air. This means that the amount of carbon dioxide in the air can go up or down. The air in some places contains a lot of pollution, and miners sometimes have to worry that they might find bad air that is poisonous when they go underground. If miners become trapped, they have to also worry that they might use up all of the oxygen in the room, so that there is no more oxygen in the air.

Thinking about all of this, what does it mean? We can have air with a lot of water, or very little water. We can have air with a lot of carbon dioxide, or very little. We can have air with a lot of pollution, or very little pollution. And we can have air with a lot of oxygen, or very little oxygen. In other words, the air can be different in the types of elements it has in it, but it is still considered to be air! So, yes, you can remove an element from the air, and it will still be air-- it will still be a mixture of gases surrounding the earth. It will just be a different kind of air!

"Air" is more a common phrase than an exact scientific description. The air around you is a mixture of many gases, including roughly 78% nitrogen, 21% oxygen, 1% argon, and trace amounts of carbon dioxide, neon, helium, methane, krypton, hydrogen, and many more chemicals. What is and isn't considered air is very much up to the people discussing it. For example, if you entered a room without the trace amounts of helium that exist in the atmosphere (there are usually about 5 helium atoms in every million atoms of air), you wouldn't even notice without a very, very sensitive instrument to detect the change, and it wouldn't interfere with your breathing or anything else. But if you took away all the oxygen from air in a room, you wouldn't be able to breathe in the room (we take in the oxygen from air to respirate) and no fires would light in the room. Many people would probably not call the atmosphere in the room "air" anymore-- they might call it "Nitrogen gas", since the remaining gases would be 98% nitrogen. But what if you only removed some of the oxygen? If would still be hard to breathe, and fires wouldn't burn as well, but you might still call it "air". Specialized forms of "air", with different mixtures of gases, are regularly used by ocean divers in their SCUBA gear. Nitrogen gas can be dangerous to the human body when under pressure in the ocean, so different "air" that can be breathed but without the dangerous nitrogen is necessary-- often, the nitrogen is replaced with much higher amounts of helium, such as in the SCUBA breathing gases "heliox" and "trimix". Using these special gas mixtures to breathe allows the divers to safely venture very deep into the ocean to explore.