Question

This substance is a powerful oxidizing agent and a harmful pollutant; yet a layer of it in the upper stratosphere serves as a shield from harmful ultraviolet radiation from the sun. What is this substance?

1) CO₂
2) O₂
3) SO₃
4) O₃ (ozone)

Answer 1

4. Ozone (O₃) is a molecule that serves as a protective shield against ultraviolet radiation in the stratosphere and is crucial for life on Earth, despite being harmful as a ground-level pollutant.

Step-by-step explanation:

The substance you're referring to is 4. ozone (O₃), which is an unstable form of oxygen with three oxygen atoms bonded together. In the upper stratosphere, a layer of ozone serves as a protective shield against harmful ultraviolet radiation from the sun, absorbing it and preventing it from reaching the Earth's surface. This process is crucial as ultraviolet radiation can damage living organisms.

Despite being a powerful oxidizing agent and harmful as a pollutant at ground level, where it can cause respiratory health problems and damage crops and ecosystems, stratospheric ozone plays a critical role in protecting life on our planet.