[seniour_baloch]

Element Definition: A chemical element is a substance that cannot be broken down by chemical means.
N2 or O2 are elements! How can't we break by chemical means.

[curiouscat]

N2 or O2 are elements

Nope. N and O are.

[seniour_baloch]

You mean that elements can't be in diatomic form?

[Arkcon]

Yes, its a bit odd, they're not elements, when found in their most stable, natural forms.  They are instead molecules, and no molecule is an element.  Think of it this way, when you're looking at a complex molecule, say, an amino acid, the presence of an oxygen here, a nitrogen there, a sulfur atom if you find it over there changes the property of the molecule.  That's what we mean when we talk about a "chemical element."

[fledarmus]

Most of our language is just a little looser than that. We use element both to refer to a single atom, and to refer to a molecule made up of a single type of atoms in their stable, neutral forms. In other words, both O and O₂ might be referred to as elemental oxygen, and C, graphite, and diamond might all be called elemental carbon.

The definition you will use depends on the context that you are using it in, and the demands of your teacher.