How many electrons are in an ion of calcium (Ca2+)? A. 2 B. 18 C. 0 D. 22
The Correct Answer and Explanation is:
The correct answer is B. 18.
Here’s the explanation:
Calcium (Ca) is an element in Group 2 of the periodic table, meaning it has 2 electrons in its outermost shell in its neutral state. The atomic number of calcium is 20, which means it normally has 20 electrons when it is neutral, to balance the 20 protons in its nucleus.
However, when calcium forms a Ca²⁺ ion, it loses two electrons from its outermost shell to achieve a stable electron configuration. The ionization process occurs because calcium tends to lose its two valence electrons in order to attain the electron configuration of the nearest noble gas, which is argon (Ar), with an atomic number of 18.
Therefore, the Ca²⁺ ion has:
- 20 protons (same as neutral calcium).
- 18 electrons (2 fewer than the neutral atom).
Since the Ca²⁺ ion has 18 electrons, the correct answer is B. 18.
This process is an example of ionization, where atoms lose or gain electrons to form charged species (ions), in this case, a positively charged ion (cation) because it lost electrons.
