17. Which of the following lists contains only elements and a reason why they are elements
C12, H2, Na, He - Substances are elements because they are pure.
H, O, NaCl, N2, CO2-Substances are elements because they
contain more than one chemical symbol
Kr, Ne, Ar, He - Substances are elements because they are all noble
gases.
F3, Os, Li, H-Substances are elements because they all have
chemical symbols.

You exhale co2 which is produced during cellular respiration.  co2 combines with the water in your blood's plasma to make up one half of the body's most important buffer pair, carbonic acid.  the more physical activity you engage in, the more co2 your body is producing.  you can see this by putting some of the cabbage indicator in a glass and then blowing bubbles into it through a straw.  can you see a change in the color of the indicator?

Who discovered a pattern to the elements in 1869?

The empirical formula of a compound is ch2o and its mass is 120 amu/molecule, what is its formula?