Period 6 element years and is used in medical applications, industrial gauges, and hydrology. Although the element is only mildly toxic, it is a hazardous material as a metal and its radioisotopes present a high health risk in case of radioactivity releases. Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in Group 2, a soft silvery metallic alkaline earth metal. Barium is never found in nature in its pure form due to its reactivity with air. Its oxide is historically known as baryta but it reacts with water and carbon dioxide and is
Relative atomic mass Relative atomic mass Relative atomic mass (symbol: "A") or atomic weight is a dimensionless physical quantity defined as the ratio of the average mass of atoms of a chemical element in a given sample to one unified atomic mass unit. The unified atomic mass unit (symbol: "u" or "Da") is defined as being of the atomic mass of a carbon-12 atom. Since both values in the ratio are expressed in the same unit ("u"), the resulting value is dimensionless; hence the value is said to be "relative". For a single given sample, the relative atomic mass of a given element