Final answer:
There are approximately 20 million known organic compounds, but the exact number is constantly changing due to new discoveries. Around 83% of the known elements are natural.
Step-by-step explanation:
The exact number of known chemicals is difficult to determine because new compounds are constantly being discovered. However, there are approximately 20 million different known organic compounds, which are carbon-containing molecules. Each day, scientists discover new organic compounds, so the number is constantly changing. As for the percentage of natural compounds, there are 98 naturally occurring elements out of the 118 known elements. This means that around 83% of the known elements are natural. Elements are represented in the periodic table with chemical symbols.