Arsenic
Atomic symbol: As
Atomic number: 33
Atomic mass: 74.92
Appearance: Gray, yellow, or black solid at 25°C
Group: 15
Period: 4
Series: Metalloids
Block: p
Electron configuration: 1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p³
Arsenic is mainly used in alloys of lead; it is being used less and less today since it is incredibly toxic.
Due to its toxicity, it is useful in pesticides, herbicides, and insecticides.
Fun Fact! Very small amounts of arsenic are actually essential to the human body for growth and nervous system health. However, above that miniscule amount arsenic is carcinogenic and then deadly as the amount absorbed increases.