a radioactive gaseous factor formed because of the disintegration of radium; the heaviest of this inert gasses; takes place naturally (especially in areas over granite) and it is considered a hazard to wellness
a radioactive gaseous element formed by the disintegration of radium; the heaviest of the inert gasses; occurs naturally (especially in places over granite) and it is considered a hazard to wellness
How would you define atomic number 86?