12. estimate the actual atomic mass of ²⁴mg.\n| isotope | mass (amu) | relative abundance (%)…

12. estimate the actual atomic mass of ²⁴mg.\n| isotope | mass (amu) | relative abundance (%) |\n|--|--|--|\n| neon - 20 | 19.992 | 90.51 |\n| neon - 21 | 20.994 | |\n| neon - 22 | | 9.22 |\n| avg. atomic mass = | | total %: |

12. estimate the actual atomic mass of ²⁴mg.\n| isotope | mass (amu) | relative abundance (%) |\n|--|--|--|\n| neon - 20 | 19.992 | 90.51 |\n| neon - 21 | 20.994 | |\n| neon - 22 | | 9.22 |\n| avg. atomic mass = | | total %: |

Answer

Explanation:

Step1: Convert percentages to decimals

$90.51% = 0.9051$, and assume the relative - abundance of Neon - 21 is $x$, then $x=1-(0.9051 + 0.0922)=0.0027$.

Step2: Calculate the average atomic mass

The formula for average atomic mass $A=\sum_{i}m_i\times p_i$, where $m_i$ is the mass of the isotope and $p_i$ is its relative abundance. $A=(19.992\times0.9051)+(20.994\times0.0027)+(21.991\times0.0922)$ $A = 19.992\times0.9051+20.994\times0.0027 + 21.991\times0.0922$ $A=18.0957692+0.0566838+2.0275702$ $A = 20.1799232\approx20.18$ amu.

Answer:

$20.18$ amu