Why is it so difficult to show the amount of carbon dioxide on a pie chart?

If the pie chart represents all the gases in the atmosphere.

Then a sector of 79% ( 284.4 degrees) is for nitrogen

A sector of 20% ( 72 degrees) represents oxygen.

This leaves 1% (3.6 degrees) for all the other gases. , which are argon, neon ,helium, krypton, water vapour, and carbomn dioxide.

Since carbon dioxide is quoted as 300 ppm ( 300 part per million parts) , then it is a very tiny amoun t of the 1% ( 0.108 (~ 1/10) degrees of arc of the circular sector)

3.6 degrees is a very narrow arc on the circle ( pie chart). Hence 0.1 degree is narrower than a straight pencil line on the same chart . So it is very difficult to show the CO2 value on a pie chart.