According to the duplet rule, a maximum of 2 electrons makes the K shell stable. Why does calcium, which has 2 electrons, react by losing 2 electrons?
Answer (1)
The question relates to the concept of electron shells and stability in chemistry. The 'duplet rule' refers to the stable configuration achieved when an atom has two electrons in its outermost shell, similar to the electron configuration of helium, which is known as a noble gas. This rule is applicable mainly for very light atoms such as hydrogen and helium.
For elements like calcium, which is an alkali earth metal found in Group 2 of the periodic table, stability through loss of electrons is explained by the 'octet rule.' Calcium has 20 electrons with the electronic configuration:
1 s 2 2 s 2 2 p 6 3 s 2 3 p 6 4 s 2
Helium and other noble gases follow the duplet or octet rule, which means they are stable with fully filled outer shells.
In the case of calcium, its atomic configuration is such that the outermost shell (the 4s orbital) contains two electrons. Calcium atoms are more stable when they have a complete octet in the second outermost shell (the 3p orbital, which is already full). By losing two electrons from the 4s orbital, calcium achieves a stable noble gas configuration similar to argon. This configuration decreases its energy state, which makes it more stable, and is the reason why calcium tends to lose two electrons when reacting.
So, in conclusion, although calcium has two electrons in its outermost shell (4s), it loses these electrons to revert to a stable electronic configuration that adheres to the octet rule, resulting in a more stable ionic state with a full 3p orbital. This tendency to achieve stability through the configuration of a noble gas is an essential principle in understanding the chemical reactivity of elements.
