Why are elements not able to be broken down into simpler substances?

This is because they are already the simplest substances.

Think about it: You can't simplify the fraction 1/2 any more because it is already in the simplest form. The same goes for elements. They cannot be broken down into simpler (or smaller) substances.

Hope this helped! Good luck! :)

Cis the

1) noble gases2) by increasing atomic number3) noble gases