What is a chemical compound?

Answer 1

Chemistry. A pure, macroscopically homogeneous substance consisting of atoms or ions of two or more different elements in definite proportions that cannot be separated by physical means. Any time you have two atoms of different elements (hydrogen, carbon, cesium, etc) bond, then you have a certifiable compound. Take carbon dioxide for example: CO2. Why is this a compound? Because it has at least two different atoms of different elements (carbon and oxygen). We also know that this is a compound because every compound of CO2 is the same (aka macroscopically homogeneous) and every compound will have a ratio of carbon to oxygen which is 1:2 (aka definite proportions).

A reasonable question would be: Well, what if it is only made of one element? Those would be called molecules. "Molecule" is an umbrella term that covers all types of situations of bonded elements. Any bonded elements can be a molecule, H2, CO2, NH4, NO2. But not all molecules can be compounds; if it does not contain two different elements, then it is simply a molecule, such as O2. All compounds are molecules, but not all molecules are compounds.

Now, we say that these atoms are bonded together to create this compound/molecule. There are many types of bonds; for more information, refer to related questions.
a substance formed by chemical union of two or more elements or ingredients in definite proportion by weight.