Задание №15335 ЕГЭ по Английскому языку

Imagine that you are preparing a project with your friend. You have found some interesting material for the presentation and you want to read this text to your friend. You have 1.5 minutes to read the text silently, then be ready to read it out aloud. You will not have more than 1.5 minutes to read it.

   Most of the elements occur in the periodic table in the order of increasing atomic weight. There still remain, however, four pairs of elements in the inverted order of atomic weight; argon and potassium, cobalt and nickel, telluruim and iodine, and protactinium and thorium. The nature of the isotopes of these elements is such that the atomic weight of the naturally occurring mixture of isotopes is greater for the element of the lower atomic number in each of these pairs than for the element of higher atomic number; thus, argon consists almost entirely (99.6%) of the isotope with mass number 40, whereas potassium consists largely (93.4%) of the isotope with mass number 39. This inversion of the order in the periodic system, as indicated by the chemical properties of the elements, from that of atomic weight caused much concern before the atomic numbers of the elements were discovered, but has now been recognized as having little significance.