Isotope Abundance

Magnesium consists of three naturally occurring isotopes. The percent abundance of  these isotopes is as follows: ²⁴Mg (78.70%), ²⁵Mg (10.13%), and ²⁶Mg (11.7%). The average atomic mass of the three isotopes is 24.3050 amu. If the atomic mass of ²⁵Mg is 24.98584 amu, and ²⁶Mg is 25.98259 amu, calculate the actual atomic mass of ²⁴Mg.  

• 23.985 amu
• 21.421 amu
• 24.463 amu
• 24.002 amu

Tags

NGSS.HS-PS1-8

 Copper occurs naturally as Cu-63 and Cu-65. Which isotope is more abundant?

• Cu-63
• Cu-65

The atomic masses and the relative abundances of 2 naturally occurring isotopes of an unknown element X are as following: isotope X-7 has a relative abundance of 95% and isotope X-10 has a relative abundance of 5%. Which of the following is correct

• (7 x 95) + (10 x 5)
• (7 x 0.95) + (10 x 0.05)
• (7 x 0.95) + (10 x 0.5)
• (0.7 x 95) + (0.10 x 5)