Period 4 element be dangerous in large enough quantities due to its radioactivity. Nickel (Ni) is an element in period 4, between cobalt and copper. Nickel is rare in the Earth's crust, mainly due to the fact that it reacts with oxygen in the air, with most of the nickel on Earth coming from nickel iron meteorites. However, nickel is incredibly common in the Earth's core; along with iron it is one of the two main components. Nickel is an important component of stainless steel, and in many superalloys. Copper (Cu) is an element in period 4, between nickel and zinc. Copper is
Lacul cu Nămol Lacul cu Nămol Lacul cu Nămol, also called (Lacul) Balta cu Nămol, is a natural salt lake in the town of Ocna Sibiului, Sibiu County, Transylvania, Romania. It is one of the many lakes of the Ocna Sibiului mine, a large salt mine which has one of the largest salt reserves in Romania. In Romanian, "Lacul cu Nămol" means "the Lake with Mud" . The other name of the lake, Balta cu Nămol, means the Pond with Mud. The lake was formed after an excavation of the salt's cover. Lacul cu Nămol and Lacul Negru are the only lakes of