Question

An atom has two electrons more than its nearest inert gas configuration. What type of ion will it form?

Answer 1

• Elements present in Group 18 or Zero Group of the periodic table are termed as noble gases or inert gases.
• All the elements of Group 18 have eight electrons in their outermost or valence shell, except Helium (He) which has only two valence electrons.
• Since the given atom has two electrons more than its nearest inert gas configuration, it means the given atom has two electrons in its outermost shell. Thus, the given atom has to either lose these two electrons to attain a noble gas configuration, or otherwise it will have to accept six more electrons to form a stable inert gas configuration.
• Adding six electrons is a very high energy-consuming process, so instead of that, it is easier to lose two electrons and achieve a noble gas configuration.
• If an atom loses electrons, it will form a positively charged ion known as a cation.
• Example, Magnesium (Mg) has an atomic number of 12 and the atomic number of Neon (Ne) which is a noble gas is 10.
• The electronic configuration of Mg and Ne is $2,8,2$ and $2,8$, respectively.
• According to the electronic configuration, it can be clearly seen that Mg has two extra electrons as compared to the noble gas (Ne). These two electrons can be easily removed to attain a stable inert gas configuration of Ne. The loss of electrons by an atom or molecule results in the formation of positively charged species termed as a cation.
• Magnesium easily loses its two valence electrons to attain a stable noble gas configuration of Neon (Ne) and forms a positively charged Magnesium cation (Mg²⁺).
• $\mathrm{Mg}\to {\mathrm{Mg}}^{2+}+2{\mathrm{e}}^{-}$
• .Hence, the type of ion formed is a cation.