Identify the symbols for the isotopes below in the X-A notation (e. g. B-10):
a. argon with 21 neutrons
b. uranium with 231 neutrons
c. nitrogen with 7 neutrons
d. bromine with 45 neutrons

• A. a) Ar-41; b) U-326; c) N-14 ; d) Br-80
• B. a) Ar-39; b) U-323; c) N-14 ; d) Br-80
• C. a) Ar-40; b) U-326; c) N-12 ; d) Br-80
• D. a) Ar-41; b) U-327; c) N-12 ; d) Br-81

Answer: (B)