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
CU Online earned through traditional on-campus courses; even if a student completes an entire program online, the degree is awarded with the same benefactor, University of Colorado. CU Online offers courses in liberal arts and science, arts and media, business, education, engineering, public affairs, and architecture and planning. Below are the complete degree programs and certificates that can be completed exclusively through online courses. CU Online CU Online is one of the first fully accredited online education programs, created in 1996 by the University of Colorado Denver (CU Denver). With CU Online, the pedagogy of CU Denver faculty has been extended globally,