A pure chemical compound is a chemical substance that is composed of a particular set of molecules or ions that are chemically bonded. Two or more elements combined into one substance through a chemical reaction, such as water, form a chemical compound.
A chemical compound can be either atoms bonded together in molecules or crystals in which atoms, molecules or ions form a crystalline lattice. Unlike elements compounds can be broken down in chemical means.
Helium Remember: electron filling of atomic shell ... The element which have electron in the lowest quantum shell will have the smallest atomic radius\
The independent variable is what you are testing in the experiment - it sounds like the independent variable in this experiment is the amount/concentration of nitrogen
