Which was the fifth element that the scientists invented on the Periodic Table?
[img=http://upload.wikimedia.org/wikipedia/commons/8/87/B-TableImage.svg] Boron (pronounced /ˈbɔərɒn/) is a chemical element with atomic number 5 and the chemical symbol B. Boron is a trivalent metalloid element which occurs abundantly in the evaporite ores borax and ulexite. Boron is never found as a free element on Earth. Boron is an essential plant nutrient, although high soil concentrations of boron may also be toxic to plants. As an ultratrace element, boron is necessary for the optimal health of rats and presumably other mammals, though its physiological role in animals is poorly understood. Elemental boron is nontoxic and common boron compounds such as borates and boric acid have low toxicity (approximately similar to table salt with the lethal dose being 2 to 3 grams per kg) and therefore do not require special precautions while handling. Some of the more exotic boron hydrogen compounds, however, are toxic as well as highly flammable and do require special care when handling.
