What rare element has an atomic number of 4, an atomic mass of 9u, and is usually formed after the collision of atomic nuclei with cosmic rays?

Beryllium (Be) was discovered in the 17th century and named by J. J. Berzelius. It does not occur free in nature, but can be found in beryl and emerald, minerals that were known to the ancient Egyptians.

Asked by Vasilii Kulev · Last updated 4 years ago · 2.3K views · SOURCE