Question

Is Earth's atmosphere an element, compound, heterogeneous mixture, or homogeneous mixture and why?

Answer 1

The atmosphere is not an element. There’s no “atmosphere” element on the periodic table because the atmosphere is made of a lot of components like nitrogen, oxygen, CO2, etc.

https://science.sciencemag.org/content/279/5354/1184

Answer 2

heterogeneous mixture - Made up of smaller parts create one element
homogeneous mixture - Made of equal parts
compound - Something that is composed of two or more elements