## Chemistry 9th Edition

$^{35}$Cl is more abundant than $^{37}$Cl
$^{37}$Cl is less abundant because the average atomic mass of Cl is 35.453, which is closer to 35 than 37. Average atomic mass takes in to consideration the mass of the isotopes as well as the relative abundances, so since the average atomic mass of Cl is 35.453, there are more $^{35}$Cl than $^{37}$Cl