4: The prefix "tetra" means "four", and the most common valence of hydrogen is 1.

4: The prefix "tetra" means "four", and the most common valence of hydrogen is 1.

Carbon is an atom.

One atom of carbon is one atom of carbon. One gram atom of carbon is the atomic weight (14 in the case of carbon) in grams, so it would be 14 grams of carbon.

The adjacent carbon atom means the carbon atom next to, or beside, the atom of interest. For example, in an aldehyde, the carbon that has the double bond to oxygen is called the carbonyl carbon. The adjacent carbon is called the alpha (α) carbon.