If CI-35 has 18 neutrons, how many neutrons are

in CI-33?

(A) 17

(B) 16

(C) 15

(D) 18

(E) 19

B. 16

Explanation:

Cl - 35 and Cl-33 have the same number of protons because it is the same element Cl.

Their masses are different because they have different number of neutrons.

Cl - 33 has 2 neutrons less than Cl-35.

35 - 33 = 2

If Cl-35 has 18 neutrons, then Cl-33 has 18-2=16 neutrons.