Question

An unknown sample of mystery element T is analyzed. According to the data 7.42% of the element is ^6T and 92.58% is ^7T. The true mass of ^6T is 6.02amu and 7.02amu for ^7T. Calculate the average atomic mass and identify the element.

Answer 1

`\boxed{\text{6.95 u; Li}}`

Step-by-step explanation:

1. Atomic mass of T

To get the atomic mass of T, you calculate the weighted average of the atomic masses of the isotopes.

That is, you multiply the atomic mass of each isotope by a number representing its relative importance (e.g.., its percent of the total).

`\begin{array}{ccrcr}\textbf{Atom} & \textbf{Mass/u} &\textbf{Percent} & \textbf{Calculation}& \textbf{Result/u}\\^(6)\text{T}& 6.02 & 7.42 & 6.02 * 0.0742 & 0.45\\^(7)\text{T}& 7.02 & 92.58 & 7.02 * 0.9258& 6.50\\& & &\text{TOTAL } = &\textbf{6.95}\\\end{array}`

2. Identity of T

Lithium has an atomic mass of 6.64 u.

Element T is lithium.