(b) The atomic number of chlorine is 17. What is the number of electrons in Cl^–?

Solution:

(a) No. of electrons in Na⁺= 10 (Since the atomic number of sodium is 11, Na⁺ will have one less electron.)

(b) No. of electrons in Cl^– = 18 (Since the atomic number of chlorine is 17, Cl^– will have one more electron.)