Carbon (from carbo "coal") is a chemical element with symbol C and atomic number 6.
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) composed of atoms from more than one element held together by chemical bonds.
A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as parentheses, dashes, brackets, commas and plus (+) and minus (−) signs.
Chlorine is a chemical element with symbol Cl and atomic number 17.
Hydrogen is a chemical element with symbol H and atomic number 1.
Propane is a three-carbon alkane with the molecular formula C3H8.