Some elements on the periodic table are oxygen, helium, arsenic and fluorine. Oxygen is an odorless, tasteless and colorless gas at room temperature, but is bright blue as a liquid. Oxygen is a very reactive element and is paramagnetic, which means it has unpaired electrons.
Helium was named after the sun (from the Greek word "helios") because the sun was where it was first discovered. It is considered a noble gas because it does not naturally react with any other element. After hydrogen, helium is the most abundant element in the universe. However, there is very little helium found on Earth because it is light enough to escape the atmosphere. At room temperature, helium is an odorless and colorless gas.
Arsenic is a brittle, shiny, silvery semi-metal and is toxic to human beings in large doses. It is used in insecticides, rat poisons and fireworks. In its form as gallium arsenide, it is also used as doping agent. Arsenic is used to make certain types of glass and as a wood preservative. During the Victorian era, it was also used medicinally.
Fluorine is the most reactive of the halogens, which also include chlorine and iodine. Its name comes from the Latin "fluere," which means to flow, and it is a greenish-yellow gas at room temperature. Fluorine is so violently reactive that it attacks steel and glass, and it is never found in its natural state.