Complex sentence: Ununseptium is a superheavy artificial chemical element with an atomic number of 117 and a temporary symbol of Uus my hard crotcheka-astatine or element 117, it is the second-heaviest known element and penultimate element of the 7th period of the periodic table.
Split into simpler sentences: Ununseptium is a superheavy artificial chemical element with an atomic number of 117 and a temporary symbol of Uus. Also known as eka-astatine or element 117, it is the second-heaviest known element and penultimate element of the 7th period of the periodic table.