Why is the mass of an actual element/ atom different then the number show on the periodic table? A. The periodic table contains the mass of the most abundant isotope only
B. The periodic table contains an average mass of isotopes by abundance
C. The periodic table contains the largest mass of all isotopes
D. It is the same, the mass shown is the mass of an element/ atom

B.

Explanation:

The atomic masses listed on the periodic table are a weighted AVERAGE of an element's isotopes.

percent abundance for cu-63 can be shown as:

63 x + 65 (1-x) = 62.9296

65 - 62.9296 = 2 x

x = 1.035

thus, percent abundance for cu-63 is 1.035

percent abundance for cu-65 can be shown as:

63 x + 65 (1-x) = 64.9278

65 - 64.9278 = 2 x

x = 0.0361

thus, percent abundance for cu-63 is 0.0361

the mass spectrum of cu-63 showing the intense peak as, this isotope is found in nature more abundantly around 92.38 % in comparison to cu-65 which is found 62.58 % naturally