Question

name:____ pd:____ chemistry u3l14_q2 ct module day 3 hw
*16.
the mass spectrum of element x is presented in the diagram above. based on the spectrum, which of the following can be concluded about element x?
(a) x is a transition metal, and each peak represents an oxidation state of the metal.
(b) x contains five electron sublevels.
(c) the atomic mass of x is 90.
(d) the atomic mass of x is between 90 and 92.
*17.
the mass spectrum of an element is represented above. which of the following is most likely the identity of the element?
(a) ga
(b) ge
(c) tm
(d) lu

Explanation:

Question 16

• Option A: Mass spectrum peaks represent isotopes (different mass numbers), not oxidation states. Eliminate A.
• Option B: Mass spectrum shows isotopes (mass/abundance), not electron sublevels. Eliminate B.
• Option C: Atomic mass is a weighted average. The tallest peak (highest abundance) is around 90, but other isotopes (92, 94, etc.) exist. So atomic mass isn’t exactly 90. Eliminate C.
• Option D: The most abundant isotope is ~90, and another significant isotope is 92. The weighted average (atomic mass) will be between 90 and 92 (since 90 is most abundant, but 92 contributes too). This makes D correct.

• First, find the mass numbers of isotopes from the spectrum: peaks at 69, 70, 71 (checking the x - axis: 69, 70, 71 have significant abundance).
• Calculate the atomic mass (weighted average). Let's assume abundances: 69 (let's say ~60%), 70 (~30%), 71 (~10%) (approx from the graph: 69 is tallest, 70 next, 71 smaller).
• Atomic mass ≈ (69×0.6)+(70×0.3)+(71×0.1) = 41.4 + 21 + 7.1 = 69.5 (approx). Now check elements:
• Ga (Gallium): Atomic mass ~69.72.
• Ge (Germanium): ~72.63.
• Tm (Thulium): ~168.93 (too big).
• Lu (Lutetium): ~174.97 (too big).
• So Ga’s atomic mass matches the approximate weighted average from the spectrum.

Answer:

D. The atomic mass of X is between 90 and 92.

Question 17