Does there exist a molecule of formule XαYβ where X and Y are elements that are also found in molecule XγYδ? I am not a chemist, but I will be explaining chemistry to some third-graders. I want to give the example of how different things can be made of the same parts, but arranged differently. My &quot;real world&quot; example is a car and a motorcycle. The car has an engine and four wheels, but we can create a different vehicle with an engine and only two wheels: we get a motorcycle. Does there exist a molecule composed of the elements $\ce{X}$ and $\ce{Y}$, where $\ce{X}$ and $\ce{Y}$ can form a different molecule when the quantities of $\ce{X}$ and/or $\ce{Y}$ atoms are different?
I was hoping to use carbon and hydrogen because the children have already heard me use those words, and $\ce{CH4}$ is a gas that will make them laugh when I tell them where it comes from. But the only $\ce{CH2}$ molecule that I could find is this, which is too complicated and unfamiliar to explain. I would prefer molecules composed of the common elements hydrogen, oxygen, carbon. I would like to avoid molecules of elements that are commonly found in their elemental state such as gold, iron, or silver as at this stage I want to reinforce the idea that we cannot see molecules with the unaided eye. I might introduce the idea that a molecule (and macromaterial) can be composed of a single element later, if this lesson goes well.
For purposes of discussion, a molecule can be defined as &quot;a discrete body composed of atoms&quot;. There is no need to address quantum chemistry, as the target audience is a third-grade classroom.
$\ce{GeF2}$ and $\ce{GeF4}$
$\ce{GeCl2}$ and $\ce{GeCl4}$
$\ce{GeBr2}$ and $\ce{GeBr4}$
$\ce{GeI2}$ and $\ce{GeI4}$
$\ce{SnF2}$ and $\ce{SnF4}$
$\ce{SnCl2}$ and $\ce{SnCl4}$
$\ce{SnBr2}$ and $\ce{SnBr4}$
$\ce{SnI2}$ and $\ce{SnI4}$
$\ce{PbF2}$ and $\ce{PbF4}$
$\ce{PbCl2}$ and $\ce{PbCl4}$
$\ce{XeF2}$ and $\ce{XeF4}$
$\ce{XeO2}$ and $\ce{XeO4}$
Silicon dihalides ($\ce{F}$, $\ce{Cl}$, $\ce{Br}$, $\ce{I}$) have also all been prepared in the gas phase, but are much less stable than the tetrahalides.