Question

Identify the least stable ion of the following.
A) $L{i^ - }$
B) $B{e^ - }$
C) ${B^ - }$
D) ${C^ - }$

Answer 1

At first we will write what data is provided into the question. We will write that when an ion is more stable than the other one. Then it will decide the stability by looking into the electronic configuration of these ions. Then we will choose the correct option.

Complete answer:
Step1. We are provided in the question with the ions of Lithium, Beryllium, Boron and Carbon. We need to find out which ion is the most stable ion.
Step2. The atomic number of lithium is three. When we add one more electron, the total electrons are four. So the electronic configuration will be:
$Li = 1{s^2},2{s^2}$
All the electrons are in its full filled shell. So it is very stable.
Step3. The atomic number of Beryllium is four. When we add one more electron, the total electrons are five. So the electronic configuration will be:
$B{e^ - } = 1{s^2},2{s^2},2{p^1}$
Now there is one electron in the P orbital which makes it very less stable.
Step4: The atomic number of Boron is five . When we add one more electron, the total electrons are six. So the electronic configuration will be:
${B^ - } = 1{s^2},2{s^2},2{p^2}$
There are two electrons in the P orbital. It makes it unstable than Lithium but more stable than Beryllium.
Step5: The atomic number of Carbon is six . When we add one more electron, the total electrons are seven. So the electronic configuration will be:
${C^ - } = 1{s^2},2{s^2},2{p^3}$
It has a half filled P orbital which makes it very stable.
Step6: So from all the above data we can understand that $B{e^ - }$ is least stable.

Hence the correct answer is option B.

Note: An ion is negatively charged when an electron is added to it. Initially at original state the proton and electrons are equal in the atom which make it neutral but adding an electron disturbs the neutrality and makes an atom negatively charged.