Carbon (C) is an element
Carbon Dioxide (CO2) is a compound
Hydrogen (H) is an element
Sodium Chloride (NaCl) is a compound
A good way to tell whether something is a compound or an element, is that in a compound there is a mixture of different elements. Like in Carbon Dioxide, the symbol is CO2. This shows the carbon (C) and oxygen (O) together. I hope i worded that well enough and this helps :)
