Use the atomic mass of lithium to calculate the relative abundances of the two isotopes. Express your answers using one decimal place. Enter your answers separated by a comma. lithium-6 abundance, lithium-7 abundance \( = \) ?

To find the relative abundances of lithium’s isotopes, we start by noting that lithium has two stable isotopes: lithium-6 and lithium-7. The atomic mass of lithium is approximately 6.94 amu. Let’s denote the abundance of lithium-6 as \( x \) and lithium-7 as \( 1 - x \). The weighted average can be set up as follows: \[ 6x + 7(1 - x) = 6.94 \] Expanding and simplifying gives: \[ 6x + 7 - 7x = 6.94 \] \[ -x + 7 = 6.94 \] \[ -x = -0.06 \] \[ x = 0.06 \] Thus, lithium-6 has an abundance of 6.0%, and since the total must equal 100%, lithium-7 has an abundance of 94.0%. So, lithium-6 abundance, lithium-7 abundance \( = \) 6.0, 94.0.