Question

The number of electrons and protons in calcium ion are respectively

• A. 20, 20
• B. 20, 18
• C. 18, 20
• D. 18, 18

Answer 1

The correct option is C

18, 20

• In a neutral atom, Atomic number = number of protons
• Number of electrons = number of protons
• Mass number = number of protons + number of neutrons
• Atomic number of calcium is 20 with electronic configuration 2, 8, 8, 2 and its mass number is 40.
• The electronic configuration of ${\mathrm{Ca}}^{+2}$ ion is 2, 8, 8.
• Hence, the number of electrons in Calcium ion is 18.
• Mass number = 40 = 20 + number of neutrons.
• Number of neutrons = 20.
• The number of electrons and protons in calcium ions are 18 and 20 respectively
• Hence option c is correct.