Cholrine has an average atomic mass of 35.45 amu. the two naturally occurring isotopes of chlorine are chlorine-35 and chlorine-37. do most chlorine atoms contain 18 neutrons or 20 neutrons? why?

let the moles of chlorine-35 is n1 and chlorine-37 is n2

now we will use the formula of average atomic mass

here let say

so here since ratio of moles of chlorine 35 and chlorine 37 is more than 1 so chlorine 35 is more in the proportion in this mixture so there is most chlorine atom consist of 18 neutrons

chlorine-35

Explanation:

We are given that Chlorine has an average atomic mass=35.45 amu

The two naturally occurring isotopes of chlorine are chlorine -35 and chlorine -37.

We have to find which isotope  most contain 18 neutrons or 20 neutrons and why.

Let

Where x= Part of chlorine-35

y=Part of chlorine-37

Then, x=a and y=1

Average atomic mass=

Using this formula

The ratio of two isotopes is 3.44 which is greater than 1.

Therefore,chlorine-35 is greater than chlorine-37 in a mixture of two isotopes.

We know that atomic number of chlorine-35 is 17.

Neutron number=35-17=18

Hence, the chlorine-35 is most which contain 18 neutrons.