Question

The mass number of an atom whose unipositive ion has 10 electrons and 12 neutrons is:​

• A. 23
• B. 22
• C. 20
• D. 21

Answer 1

The correct option is A 23

Number of electrons in ($X^{+})$ = 10​

Number of electrons in X = 11​
Number of protons in X = 11​
Number of neutrons in X = 12​

• Mass number = number of protons + number of neutrons

Mass number of X = 11+12 = 23
Therefore, mass number = 23

Hence, correct option is (a)