Question

a new element has two isotopes, one with a mass of 40.0 amu and the other with a mass of 42.0 amu. the atomic weight is 40.50 g/mol. pick the true statement a. the isotope at 42.0 amu is less abundant b. the element has 19 protons and 21 neutrons c. the isotope at 40.0 amu is less abundant d. both isotopes are equally abundant e. the element has 20 protons and 21 electrons f. there is not enough information given g. the element is calcium

Answer 1

The isotope with a mass of 42.0 amu is less abundant because the atomic weight of the element is closer to the mass of the other isotope, 40.0 amu. We lack sufficient information to determine the element's number of protons, neutrons, and electrons, or to confirm if the element is calcium.

Step-by-step explanation:

The question concerns the relative abundance of isotopes and their contribution to the atomic weight of a new element. Given that the atomic weight is 40.50 g/mol, which is very close to the mass of one of its isotopes (40.0 amu), and the other isotope has a mass of 42.0 amu, we can infer that the isotope with the lower mass is more abundant because the average atomic weight is closer to it. Therefore, statement (a) 'the isotope at 42.0 amu is less abundant' is true.

To determine the number of protons and neutrons in an isotope, we would need to know the exact element, which is not provided in the question. However, since statement (g) 'the element is calcium' cannot be true without the atomic number (number of protons), which defines an element, we cannot confirm this without additional information. Therefore, all other statements regarding the number of protons, neutrons, and electrons cannot be confirmed as true or false based on the given information.

Answer 2

Statement A, "the isotope at 42.0 amu is less abundant", is true. This is because atomic weight is calculated using the relative abundances of the isotopes. Since the calculated weight is closer to the 40.0 amu isotope, this means that it must be more abundant.
Although the number of protons and neutrons add up, this statement is not necessarily true just because we know the atomic mass.