He proposed a new theory about cosmology.

He is interested in the design of spacecraft.

He is excited about living in outer space.

Radioactive elements are produced in nature and scientific experiments.

The pH of this liquid is 7.

Arsine is a colorless, odorless, and highly toxic gas.

Lithium hydride plays an important role in chemical reactions.

Hydrogen peroxide is often used for disinfecting wounds.

Tritium is one of the radioactive isotopes.

The space probe discovered a new planet.