Question

describing elements
use the drop - down menu to complete the sentence.
when 1 carbon atom combines with 2 oxygen atoms, the resulting substance is called a(n)
drop - down menu options: element, compound, isotope, ion

Explanation:

A compound is a substance formed when two or more different elements chemically combine. Carbon (C) and oxygen (O) are distinct elements; when 1 carbon atom bonds with 2 oxygen atoms, they form carbon dioxide ($CO_2$), which fits the definition of a compound. An element is a single type of atom, an isotope is a variant of an element with a different neutron count, and an ion is a charged atom/molecule, none of which match this scenario.

Answer:

compound